This change switches the time fields (firstSeen/lastSeen) of an
address from uint64 to int64, to be compatible with (time.Time).Unix,
as well as changing the block height fields (firstBlock/lastBlock)
from uint32 to int32, since block height is normally represented
signed.
This is a big change that also many general fixes to problems found
when creating transactions. In particular the Utxo and Tx formats and
serialization functions were updated with additional information that
would be necessary for rolling back old utxo and tx data data after
btcd chain switches. This change also implements the json methods
'sendfrom' and 'sendmany' to create a new transaction based on a
frontend request.
Transactions are currently not sent to btcd since the tx relay code is
not finished yet, so a temporary error is returned back to frontends
who try to send new transactions.
