* Make `decl_error!` errors usable

This pr implements support for returning errors of different pallets in
a pallet. These errors need to be declared with `decl_error!`.

The pr changes the following:

- Each dispatchable function now returns a `DispatchResult` which is an
alias for `Result<(), DispatchError>`.
- `DispatchError` is an enum that has 4 variants:
  - `Other`: For storing string error messages
  - `CannotLookup`: Variant that is returned when something returns a
  `sp_runtime::LookupError`
  - `BadOrigin`: Variant that is returned for any kind of bad origin
  - `Module`: The error of a specific module. Contains the `index`,
  `error` and the `message`. The index is the index of the module in
  `construct_runtime!`. `error` is the index of the error in the error
  enum declared by `decl_error!`. `message` is the message to the error
  variant (this will not be encoded).
- `construct_runtime!` now creates a new struct `ModuleToIndex`. This
struct implements the trait `ModuleToIndex`.
- `frame_system::Trait` has a new associated type: `ModuleToIndex` that
expects the `ModuleToIndex` generated by `construct_runtime!`.
- All error strings returned in any module are being converted now to `DispatchError`.
- `BadOrigin` is the default error returned by any type that implements `EnsureOrigin`.

* Fix frame system benchmarks

* Rename: Phase 1.

* Unify codec.

* Fixing: Phase 2

* Fixing: Phase 3.

* Fixing: Phase 4.

* Fixing: Phase 5.

* Fixing: Phase 6.

* Fixing: Phase 7.

* Fixing: Phase 8. Tests

* Fixing: Phase 9. Tests!!!

* Fixing: Phase 10. Moar tests!

* Finally done!

* More fixes.

* Rename primitives:: to sp_core::

* Apply renames in finality-grandpa.

* Fix benches.

* Fix benches 2.

* Revert node-template.

* Fix frame-system in our modules.

* primitives/sr-io -> primitives/io

* fix

* rename

* runtime-io -> sp-io

* git mv

* fix ci

* remove package name

* fix

* fix

* try minimizing diff

* try minimizing diff again

* try minimizing diff again

* Adding script for rename, could be applicable for nodes on top of it, too

* add stderr and gitlab ci features

* apply script

* fix now minor details in expected stderr

* Update the Cargo.lock

* fix name: sc-transaction -> sc-tracing

* fix rename in script, too

* Use Weight instead of u32 everywhere

* Revert Weight declaration

* Fix benches

* define slashing spans

* tests and pruning for slashing-spans record

* validators get slashed before nominators

* apply slash to nominators as well

* chill and end slashing spans

* actually perform slashes

* integration (tests failing)

* prune metadata

* fix compilation

* some tests for slashing and metadata garbage collection

* correctly pass session index to slash handler

* test span-max property for nominators and validators

* test that slashes are summed correctly

* reward value computation

* implement rewarding

* add comment about rewards

* do not adjust slash fraction in offences module

* fix offences tests

* remove unused new_offenders field

* update runtime version

* fix up some docs

* fix some CI failures

* remove no-std incompatible vec! invocation

* try to fix span-max rounding error

* Update srml/staking/src/slashing.rs

Fix type: winow -> window

Co-Authored-By: Tomasz Drwięga <[email protected]>

* slashes from prior spans don't kick validator again

* more information for nominators, suppression

* ensure ledger is consistent with itself post-slash

* implement slash out of unlocking funds also

* slashing: create records to be applied after-the-fact

* queue slashes for a few eras later

* method for canceling deferred slashes

* attempt to fix test in CI

* storage migration for `Nominators`

* update node-runtime to use SlashDeferDuration

* adjust migration entry-points somewhat

* fix migration compilation

* add manual Vec import to migration

* enable migrations feature in node-runtime

* bump runtime version

* update to latest master crate renames

* update to use ensure-origin

* Apply suggestions from code review

use `ensure!`

Co-Authored-By: Gavin Wood <[email protected]>

* fix multi-slash removal

* initialize storage version to current in genesis

* add test for version initialization

* palette -> frame

* PALETTE, Palette -> FRAME

* Move folder pallete -> frame

* Update docs/Structure.adoc

Co-Authored-By: Benjamin Kampmann <[email protected]>

* Update docs/README.adoc

Co-Authored-By: Benjamin Kampmann <[email protected]>

* Update README.adoc

* /paint to /palette

* rename paint to palette

* rename the modules in palette to be pallets

* update Structure.adoc

* bump impl

* fix CI directory

* Update docs/Structure.adoc

Co-Authored-By: Benjamin Kampmann <[email protected]>

* Adding first rough ouline of the repository structure

* Remove old CI stuff

* add title

* formatting fixes

* move node-exits job's script to scripts dir

* Move docs into subdir

* move to bin

* move maintainence scripts, configs and helpers into its own dir

* add .local to ignore

* move core->client

* start up 'test' area

* move test client

* move test runtime

* make test move compile

* Add dependencies rule enforcement.

* Fix indexing.

* Update docs to reflect latest changes

* Moving /srml->/paint

* update docs

* move client/sr-* -> primitives/

* clean old readme

* remove old broken code in rhd

* update lock

* Step 1.

* starting to untangle client

* Fix after merge.

* start splitting out client interfaces

* move children and blockchain interfaces

* Move trie and state-machine to primitives.

* Fix WASM builds.

* fixing broken imports

* more interface moves

* move backend and light to interfaces

* move CallExecutor

* move cli off client

* moving around more interfaces

* re-add consensus crates into the mix

* fix subkey path

* relieve client from executor

* starting to pull out client from grandpa

* move is_decendent_of out of client

* grandpa still depends on client directly

* lemme tests pass

* rename srml->paint

* Make it compile.

* rename interfaces->client-api

* Move keyring to primitives.

* fixup libp2p dep

* fix broken use

* allow dependency enforcement to fail

* move fork-tree

* Moving wasm-builder

* make env

* move build-script-utils

* fixup broken crate depdencies and names

* fix imports for authority discovery

* fix typo

* update cargo.lock

* fixing imports

* Fix paths and add missing crates

* re-add missing crates

* Initial draft that compiles

* Extract payment stuff from balances

* Extract multiplier update stuff from system

* Some fixes.

* Update len-fee as well

* some review comments.

* Remove todo

* bump

* Move `Externalities` into `substrate-externalities`

- `Externalities` now support generic extensions
- Split of `primtives-storage` for storage primitive types

* Move the externalities scoping into `substrate-externalities`

* Fix compilation

* Review feedback

* Adds macro for declaring extensions

* Fix benchmarks

* Introduce `ExtensionStore` trait

* Last review comments

* Implement it for `ExtensionStore`

* Signed transactions now has affinity with runtime versions

* Bump runtime version

* Remove offline slashing logic from staking.

* Initial version of reworked offence module, can report offences

* Clean up staking example.

* Commit SlashingOffence

* Force new era on slash.

* Add offenders in the SlashingOffence trait.

* Introduce the ReportOffence trait.

* Rename `Offence`.

* Add on_before_session_ending handler.

* Move offence related stuff under sr-primitives.

* Fix cargo check.

* Import new im-online implementation.

* Adding validator count to historical session storage as it's needed for slash calculations

* Add a comment about offence.

* Add BabeEquivocationOffence

* GrandpaEquivocationOffence

* slash_fraction and fix

* current_era_start_session_index

* UnresponsivnessOffence

* Finalise OnOffenceHandler traits, and stub impl for staking.

* slash_fraction doesn't really need &self

* Note that offenders count is greater than 0

* Add a test to ensure that I got the math right

* Use FullIdentification in offences.

* Use FullIndentification.

* Hook up the offences module.

* Report unresponsive validators

* Make sure eras have the same length.

* Slashing and rewards.

* Fix compilation.

* Distribute rewards.

* Supply validators_count

* Use identificationTuple in Unresponsivness report

* Fix merge.

* Make sure we don't slash if amount is zero.

* We don't return an error from report_offence anymo

* We actually can use vec!

* Prevent division by zero if the reporters is empty

* offence_forces_new_era/nominators_also_get_slashed

* advance_session

* Fix tests.

* Update srml/staking/src/lib.rs

Co-Authored-By: Robert Habermeier <[email protected]>

* slashing_performed_according_exposure

* Check that reporters receive their slice.

* Small clean-up.

* invulnerables_are_not_slashed

* Minor clean ups.

* Improve docs.

* dont_slash_if_fraction_is_zero

* Remove session dependency from offences.

* Introduce sr-staking-primitives

* Move offence under sr_staking_primitives

* rename session_index

* Resolves todos re using SessionIndex

* Fix staking tests.

* Properly scale denominator.

* Fix UnresponsivnessOffence

* Fix compilation.

* Tests for offences.

* Clean offences tests.

* Fix staking doc test.

* Bump spec version

* Fix aura tests.

* Fix node_executor

* Deposit an event on offence.

* Fix compilation of node-runtime

* Remove aura slashing logic.

* Remove HandleReport

* Update docs for timeslot.

* rename with_on_offence_fractions

* Add should_properly_count_offences

* Replace ValidatorIdByIndex with CurrentElectedSet

ValidatorIdByIndex was querying the current_elected set in each call, doing loading (even though its from cache), deserializing and cloning of element.

Instead of this it is more efficient to use `CurrentElectedSet`. As a small bonus, the invariant became a little bit easier: now we just rely on the fact that `keys` and `current_elected` set are of the same length rather than relying on the fact that `validator_id_by_index` would work similar to `<[T]>::get`.

* Clarify babe equivocation

* Fix offences.

* Rename validators_count to validator_set_count

* Fix squaring.

* Update core/sr-staking-primitives/src/offence.rs

Co-Authored-By: Gavin Wood <[email protected]>

* Docs for CurrentElectedSet.

* Don't punish only invulnerables

* Use `get/insert` instead of `mutate`.

* Fix compilation

* Update core/sr-staking-primitives/src/offence.rs

Co-Authored-By: Gavin Wood <[email protected]>

* Update srml/offences/src/lib.rs

Co-Authored-By: Robert Habermeier <[email protected]>

* Update srml/im-online/src/lib.rs

Co-Authored-By: joe petrowski <[email protected]>

* Update srml/im-online/src/lib.rs

Co-Authored-By: joe petrowski <[email protected]>

* Update srml/im-online/src/lib.rs

Co-Authored-By: joe petrowski <[email protected]>

* Update srml/babe/src/lib.rs

Co-Authored-By: joe petrowski <[email protected]>

* Update core/sr-staking-primitives/src/offence.rs

Co-Authored-By: joe petrowski <[email protected]>

* Update core/sr-staking-primitives/src/offence.rs

Co-Authored-By: joe petrowski <[email protected]>

* Update core/sr-staking-primitives/src/offence.rs

Co-Authored-By: joe petrowski <[email protected]>

* Update core/sr-staking-primitives/src/offence.rs

Co-Authored-By: joe petrowski <[email protected]>

* Update core/sr-staking-primitives/src/offence.rs

Co-Authored-By: joe petrowski <[email protected]>

* Add aura todo.

* Allow multiple reports for single offence report.

* Fix slash_fraction calculation.

* Fix typos.

* Fix compilation and tests.

* Fix staking tests.

* Update srml/im-online/src/lib.rs

Co-Authored-By: Logan Saether <[email protected]>

* Fix doc on time_slot

* Allow slashing only on current era (#3411)

* only slash in current era

* prune journal for last era

* comment own_slash

* emit an event when old slashing events are discarded

* Pave the way for pruning

* Address issues.

* Try to refactor collect_offence_reports

* Other fixes.

* More fixes.