Validate post-block state root

[perama-v]

At present the state data (proof) is for the block prior to the current block. The block transactions are applied to this state. That
results in the state root in the current block.

The proof from the prior block can be updated by tracking the state changes after each transaction. After the last
transaction the state root can be checked to match that which is in the header.

[perama-v]

Related: #6