Added PutBlockReceipts; storing receipts by blocks. Eventually this will
require pruning during some cleanup cycle. During forks the receipts by
block are used to get the new canonical receipts and transactions.
This PR fixes#1473 by rewriting transactions and receipts from the point
of where the fork occured.
* Miners do now verify their own header, not their state.
* Changed old putTx and putReceipts to be exported
* Moved writing of transactions and receipts out of the block processer
in to the chain manager. Closes#1386
* Miner post ChainHeadEvent & ChainEvent. Closes#1388
