New Block Structure for transaction decoupling #1

[Bigpiggy01]

Since transactions that are flagged/moved to buspool hash been validated, blocks no longer need to include raw transactions but instead only include transaction hash (txid). Therefore we need to modify the new block structure to take this into consideration.
Header: nothing change
Body:
vtx : raw transactions vector (coinbase and tx from mempool)
Vtxid (tx from buspool): transaction hash / txid vector if block version “flagged” that it supports it. We can either use VERSIONBITS_TOP_BITS or mask certain bit in nVersion of the block header for this flag.