* Fix error handling in sandboxing/contracts modules

* Add some docs.

* Add some tests.

* grammar

* Implement codec for U256

* Use little endian and add tests

* Extract well known keys into a single place

* Fixes.

* changes_trie

* changs_trie: continue

* changes_trie: adding tests

* fixed TODO

* removed obsolete ExtrinsicChanges

* encodable ChangesTrieConfiguration

* removed polkadot fle

* fixed grumbles

* ext_storage_changes_root returns u32

* moved changes trie root to digest

* removed commented code

* read storage values from native code

* fixed grumbles

* fixed grumbles

* missing comma

* First effort

* API versioning

* Introduce validate_transaction

* Introduce the API plus fixes.

* Docs

* Typo

* Add longevity parameter to transaction validity info.

* Telemetry Refactor

* Cleanup

* Sleep after clearing Sender on error

* Make `system` module renamable in `impl_outer_event!`

* Implement `construct_runtime!` macro

This macro generates code for calling all the common `impl_outer_*` macros.

* Add documentation

* Fixes wrong declaration of `contract`

* Update dependencies to work on `no_std`

* One more `Cargo.lock` update

* Address comments

* Not use extern

* Update Cargo.lock

* WIP

* Direct return of output data.

* Docs and renamings.

* Add get_storage test.

* Overwrite the scratch buffer.

* Add --locked to the cargo build

* Remove trailing spaces

* Update Cargo.lock

* treasury: use 'mutate' and 'retain' to avoid creating a new vec

* treasury: check the underflow case

* Fixed spelling and grammar for clarity

* Update README.adoc

* Three comma club

* gramma grammma grammar

* Update README.adoc

* Remove commas

Corrected the commas.

Consider the sentences:

- "Energy-saving light bulbs which are cheap make for a sensible investment"
- "Energy-saving light bulbs, which are cheap, make for a sensible investment"

They are different. The first one is intimating that energy-saving light bulbs come in many prices and it's only the cheap ones which are a good investment. The second implies that all energy-saving light bulbs are generally cheap and they, regardless of price, make for a good investment.

The commas added (which I just removed) switched the meaning, incorrectly, from one to the other.

* bugfix: balances::transfer for new_account

issue:#722
would_create flag should depend on dest, not origin.
change 
```rust
let would_create = from_balance.is_zero();
```
to 
```rust
    let to_balance = Self::free_balance(&dest); 
    let would_create = to_balance.is_zero(); 
```
in the other hand, provide `fn new_test_ext2()` and let `transfer_fee=10`, `creation_fee=50` for test case

* Update lib.rs

* Update tests.rs

* Make `impl_outer_origin!` support generic `Origin`s (#732)

* Make `impl_outer_origin!` support generic `Origin`s

* Support empty outer origin

* Contracts: fix transfer function. (#733)

* Remove dependency on the parity repo (#734)

* Fix test

* Anothe fix

* Remove redundant code and merge rest into rt-std

* Update lib.rs

* Make `impl_outer_origin!` support generic `Origin`s

* Support empty outer origin