Re-creating the transaction on the cold wallet was not splitting
the change, causing the transaction to be rejected by the network.
This worked on testnet since amounts do not have to be split.
Also add selected_transfers, which can now be saved since they're
size_t rather than iterators. This allows the view wallet to
properly set the sent outputs as spent and update balance.
Bump transfer file version numbers to match.
31abac4daf