JSON-RPC interface

[BelfordZ]

I would like to add ipfs to https://github.com/etclabscore/jade-service-runner and it would be much easier if there was a JSON-RPC interface, and EVEN more easy if it had an OpenRPC document / service discovery implemented.

There are a lot of ways this could be implemented, I'm not familiar enough with this codebase to make the call on what may be the best way.

[Stebalien]

While this would definitely be useful, it would be a sizable undertaking and isn't really the direction we'd like to take our RPC interface. We're planning on revamping the API transport however:

1. We handle a significant amount of binary data so the encoding will likely be CBOR, not JSON. Binary data in JSON is currently a big pain point for us.
2. Many of our commands need to stream responses. JSON-RPC doesn't support this.