Fix some remaining issues with reported balances.

CalculateBalance now works correctly: if confirmations is 0, all UTXOs
will be used for the balance.  Otherwise, unconfirmed UTXOs will be
exclused.  1 confirmation will allow the UTXO height and current block
height to be equal.  Even though the difference is zero, the
transaction including the UTXO has been mined into one block.

This change also remove extraneous account balance notifications for
connected and disconnected blocks.