We make it explicit in the appropriate Block/Transaction structures, not via a
singleton as C# node does. I think this approach has a bit more potential and
allows better packages reuse for different purposes.
Our block.Block was JSONized in a bit different fashion than result.Block in
its NextConsensus and Index fields. It's not good for notifications because
third-party clients would probably expect to see the same format. Also, using
completely different Block representation is probably making our client a bit
weaker as this representation is harder to use with other neo-go components.
So use the same approach we took for Transactions and wrap block.Block which is
to be serialized in proper way.
Fix `Script` JSONization along the way, 3.0 node wraps it within `witnesses`.
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
