[enh] add support for multiple outputs
Allows Silkaj to make a transaction to multiple receivers using a new separator in
--output=<public key>[:checksum][,<public key>[:checksum]]
So the transaction's
--amount is sent to each output, which means if we send
--amount 10 with 3 outputs we actually send 30.
I've tried to integrate it without many modifications as I don't know the possible impacts elsewhere.