* 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
* core: Added GasPriceChange event
* eth: When one of the DB flush methods error a fatal error log message
is given. Hopefully this will prevent corrupted databases from
occuring.
* miner: remove transactions with low gas price. Closes#906, #903