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

Add RPC/Websocket calls for:

getdepositscript
createseries
replaceseries
thawseries
I was going to suggest returning (string, error) here as there's no reason to return interface{} -- you can still just pass the return value of this function as the return value of GetDepositScript, but I see you've merged the branch yourself. Not really nice, but whatever