[tracking-issue] Electrum Protocol catch-up

[Davidson-Souza]

We have two versions of Electrum to implement: 1.6 and 1.7, this issue tracks what we need to get them working. It will be updated as progress goes, and if the plan changes during work.

Version 1.6:

New RPCs:

• blockchain.transaction.broadcast_package (blocked by mempool work)
• mempool.get_info (blocked by mempool work)

Changes to existing RPCs:

• server.version is now required, and should be the first message sent over the channel. It should also allow unknown arguments for protocol extensibility.
• Specific ordering for unconfirmed transactions in blockchain.scripthash.get_mempool and during status hash computation
• optional mode argument added to blockchain.estimatefee
• blockchain.block.headers now returns headers as a list, instead of a single concatenated hex string.

Version 1.7

New RPCs:

• blockchain.scriptpubkey.*
• blockchain.outpoint.subscribe
• blockchain.transaction.testmempoolaccept (blocked by mempool work)
• mempool.recent (blocked by mempool work)

Changes to existing RPCs:

• Changes to server.ping