Reduction of the block structure size (droppting unnecesary fields, etc. ..)

[pbukva]

ValidatorsHash: this value represents hash of whole set of validators which participated on DKG round valid for the CURRENT eon (which is still in proggress).
This value does not need to present in the each block, it is enough to be present only in single block where DKG round has been concluded. Blocks which depend on it can keep only block index as reference.

NextValidatorsHash: this value represents hash of whole set of validators which participated on DKG round valid for the NEXT eon (which has NOT started yet).
This value does not need to present in the each block, it is enough to be present only in single block where DKG round has been concluded. Blocks which will depend on it can keep only block index as reference.

ConsensusHash: This value represents has of the concesus configuration structure, which should not change during eon. Thus, this value could be present only in the block where configuration changed the last time, and following blocks can store only the index to that block.