Interface ValidatorHistoricalRewards

ValidatorHistoricalRewards represents historical rewards for a validator. Height is implicit within the store key. Cumulative reward ratio is the sum from the zeroeth period until this period of rewards / tokens, per the spec. The reference count indicates the number of objects which might need to reference this historical entry at any point. ReferenceCount = number of outstanding delegations which ended the associated period (and might need to read that record)

• number of slashes which ended the associated period (and might need to read that record)
• one per validator for the zeroeth period, set on initialization