Implement getreceivedbyaddress RPC.

Unlike Bitcoin Core wallet, this implementation does not ignore
coinbase transactions.
Fix a couple comments
Changed TxIn.PreviousOutpoint to TxIn.PreviousOutPoint.
Removed hashType byte cast.
Update for recent btcec API changes.

This change is introduced so that btcwallet will continue to compile after
issue 6 in btcec is merged.