* Update vesting spec and impl time fields and constructors
* Update genesis to support vesting accounts
* More spec and godoc updates
* Update genesis section in vesting spec
* Fix bank unit tests
* Add test cases to ToAccount in genesis
* Update RegisterCodec to include vesting interface and types
* Fix GetVestedCoins bug where block time is past vesting end time
* Add vesting accounts to simulation
* Update vesting genesis logic to panic on invalid accounts
* Change randomness of vesting accounts in simulation