Prior to this commit, users setting the POLICY config
option `tx_broadcast` to anything other than `self` would
cause a crash after the merge of #536 due to a bin/hex
conversion failure (before this merge, the tx would simply
fail to broadcast).
This commit adds a `JMTXBroadcast` AMP command so that makers
can send arbitrary transactions from daemon to client, for
broadcast via the blockchain interface. This allows the
existing code in `taker.push()` to function correctly, after
fixing the bin/hex conversion bug. Hence users can now select
`random-peer` or `not-self` and the transaction will be
broadcast as expected according to the comments, and the
WalletService will react to the broadcast just as it does
currently for self-broadcast.
Note that this change will be ineffective if the counterparties
do not support it; the transaction will simply remain un-broadcast.
Adam Gibson
d209d4d257