Use raw transactions

Use raw transactions instead of SendFromMinConf. Also stop using account
balance updates since by using listunspent we can determine if a wallet
has funds to spend.
Go doesn't have the concept of an uninitialized variable.  So if it was used outside of the select, it would either be some previous address that was set by the select, or nil.

It's a scoping issue.  If it's not intended to be used outside of some scope, don't declare it there.