1. Removes state variables:
- totalWeightedStakeThisEpoch
- totalFeesCollectedThisEpoch
- numActivePoolsThisEpoch
2. No longer indexes by epoch % 2
3. Renamed event StakingPoolActivated → StakingPoolEarnedRewards.
4. Renamed structs:
- ActivePool → PoolStats. This holds stats for a pool that earned rewards.
- UnfinalizedState → AggregatedStats. This aggregates stats from the former struct.
- No longer an upper limit on how many makers can be in a pool.
- No longer a handshake for a maker to join a pool.
- No longer any special powers given to makers.
- Pool Id starts at 1 and increments by 1.
`@0x/contracts-staking`: Convert all rewards to WETH.
`@0x/contracts-staking`: Style changes.
`@0x/contracts-staking`: Address misc. review comments.
`@0x/contracts-staking`: Make `LibFractions` scaling a separate step.
`@0x/contracts-staking`: Merge `exchange_fees` unit tests into `protocol_fees` unit tests.
`@0x/contracts-staking`: Remove `ProtocolFeeActor` and any use of it.
`@0x/contracts-staking`: Remove unused constants.
`@0x/contracts-staking`: Move WETH assertion constructor into `MixinDeploymentConstants`.
`@0x/contracts-staking`: Add more unit tests.