Add methods for processing btc transactions locally

[Senyoret1]

There are some methods of the btcd rpc API that would be good to implement in a local daemon or helper library. If a daemon is going to be created for giving compatibility with software wallets, the methods can be implemented there. The methods are in the documentation for the rpc API: https://github.com/btcsuite/btcd/blob/master/docs/json_rpc_api.md

The currently identified methods are:

• createrawtransaction
• decoderawtransaction
• validateaddress

Those methods would be used for the integration with hw wallets, so would be needed even if the daemon has methods for automatically creating transactions with software wallets.