* Add accumulators
* Move accumulator back to keeper package
* Add earn specific accumulators
* Move store methods to sub-package
* Move earn accumulator
* Rename accumulator files
* Add store doc comment
* Add earn accumulator tests, panic if accumulator not used with earn claim type
* Update earn accumulator tests to use new methods
* Add staking test for earn accumulator
* Add test for accumulator proportional rewards
* Remove old copy of GetProportionalRewardsPerSecond
* Add test for basic accumulator
* Fix AddIncentiveMultiRewardPeriod replacement
* Deduplicate base earn reward accumulator
* Check errors in tests
* Validate RewardPeriods in Params.Validate()
* Use adapter to fetch earn total shares
* Add methods for reward accrual time
* Add accrual time methods
* Add claim type to IterateAllRewardAccrualTimes callback method
* Use new AccrualTime proto type for state methods, add to genesis
* Add GetAllRewardAccrualTimes doc
* Add accrual times to genesis methods
* Remove DecodeKeyPrefix
* Update acrual time iterate method naming
* Update Iterate claims naming
* Use method for sourceID key conversion