Add HD Wallet integration (temporary and hacky!!!)

Add RPC/Websocket calls for:

getdepositscript
createseries
replaceseries
thawseries
But as I pointed out, we only need the wallet for its Manager, which can be easily created, so if we moved the code into functions that take only a Manager and btcjson.Cmd as arguments, those could easily be tested. And then here we'd just call those functions