tests: code formatting
Wallet: remove txId:index storage for spent outputs
Wallet: store txHash, vout separately instead of "from: txid:vout"
bufferutils: add Buffer reverse
Wallet: revert 2f00c9a
Wallet: consistent variable naming
Wallet: rename outputs to unspentsMap
Wallet: refactor to use Array unspents solely, deprecating unspentsMap
tests: avoid use of deprecated APIs
Merge pull request #262 from dcousens/wallref

processTx considered harmful followup