Add a JSON-RPC listener port and listener component

[mpguerra]

Motivation

zcashd's JSON-RPC interface is mainly JSON-RPC-v1, but with error handling backported from JSON-RPC-v1.1.

We plan to use jsonrpc_core with:

• jsonrpc_http_server
• jsonrpc-derive

It is async and uses hyper, which Zebra already uses.

Example Code

Here are examples of:

• setting up a HTTP JSON-RPC server
• re-using an existing tokio executor
• configuring compatibility with JSON-RPC v1 and v2
• declaring RPC methods as Rust functions

Tasks

• set up the listener port component
• make sure it works with lightwalletd

[ftm1000]

Hey team! Please add your planning poker estimate with ZenHub @conradoplg @dconnolly @gustavovalverde @jvff @oxarbitrage @teor2345 @upbqdn