1. Dropped `Base.ConsensusData` block field
2. Added `Block.ConsensusData` field with `Nonce` and `PrimaryIndex`
3. Removed "Neo.Header.GetConsensusData" and
"AntShares.Header.GetConsensusData" interops
Frequently one needs to check if struct serializes/deserializes
properly. This commit implements helpers for such cases including:
1. JSON
2. io.Serializable interface