Transaction format changed
Original change in https://github.com/ucoin-io/ucoin/issues/68
This change is mainly here to allow crosschain transactions.
Concretely, the way a transaction's outputs are affected to someone is no more always true, it does not have to have explicit recipients. Instead, it can have a password to spend the coins for example.
The whole change is rather big, so I let the protocol explain it: https://github.com/ucoin-io/ucoin/blob/master/doc/Protocol.md#transaction