Add ability to track JoinMarket wallets

[meeDamian]

They have a bit different HD wallet structure, that is incompatible with the app - it would be fantastic to be able to add and track JoinMarket wallets, and it might bring you more users from the growing community of makers there.

Here's an overview on how their wallets work: https://github.com/JoinMarket-Org/joinmarket/wiki/Using-the-JoinMarket-internal-wallet

And a (python) script that manages wallets: https://github.com/JoinMarket-Org/joinmarket/blob/master/wallet-tool.py

[stachrom]

with jm v0.5.5 (segwit wallet -> m/49'/0'/0'/1/1) may its working.
https://github.com/JoinMarket-Org/joinmarket-clientserver