getbalance: additional balance fixes (#565)
getbalance: additional balance fixes (#565)

- Include immature coinbase credits
- SSTXs are not coinbase rewards
- Also include unconfirmed in the total.
- Correctly add normal transactions to Spendable when minConf==0
- Handle unmined stake transactions properly.
jrick/dcrwallet,decred/dcrwallet,jrick/btcwallet,jrick/dcrwallet,decred/dcrwallet,jrick/btcwallet