Enumeratable accounts (#195)

* Merge remote-tracking branch 'origin/master' into gav-xts-dont-panic

* Update wasm.

* consensus, session and staking all panic-safe.

* Democracy doesn't panic in apply.

* Fix tests.

* Extra helper macro, council depanicked.

* Fix one test.

* Fix up all council tests. No panics!

* Council voting depanicked.

* Dispatch returns result.

* session & staking tests updated

* Fix democracy tests.

* Fix council tests.

* Fix up polkadot parachains in runtime

* Fix borked merge

* More Slicable support

Support general `Option` and array types.

* Basic storage types.

* Existential deposit for contract creation

* Basic implemnetation along with removals

* Fix tests.

* externalities builder fix.

* Tests.

* Fix up the runtime.

* Fix tests.

* Add generic `Address` type.

* Initial function integration of Address into Extrinsic.

* Fix build

* All tests compile.

* Fix (some) tests.

* Fix signing.

* Push error.

* transfer can accept Address

* Make Address generic over AccountIndex

* Fix test

* Make Council use Address for dispatch.

* Fix build

* Bend over backwards to support braindead derive.

* Repot some files.

* Fix tests.

* Fix grumbles

* Remove Default bound

* Fix build for new nightly.

* Make `apply_extrinsic` never panic, return useful Result.

* More merge hell

* Doesn't build, but might do soon

* Serde woes

* get substrate-runtime-staking compiling

* Polkadot builds again!

* Fix all build.

* Fix tests & binaries.

* Reserve some extra initial byte values of address for future format changes

* Make semantic of `ReservedBalance` clear.

* Fix panic handler.

* Integrate other balance transformations into the new model

Fix up staking tests.

* Fix runtime tests.

* Fix panic build.

* Tests for demonstrating interaction between balance types.

* Repot some runtime code

* Fix checkedblock in non-std builds

* Get rid of `DoLookup` phantom.

* Attempt to make transaction_pool work with lookups.

* Remove vscode settings

* New attempt at making transaction pool work.

* It builds again!

* --all builds

* Fix tests.

* New build.

* Test account nonce reset.

* polkadot transaction pool tests/framework.

* Address grumbles.

* Revert bad `map_or`

* Rebuild binaries, workaround.

* Avoid casting to usize early.

* reenable sync tests