Formalize REST JSON responses

[qstokkink]

Right now our REST API is very fluid: whatever is returned is returned. We should have a stricter API than this. This is especially bothersome as json crashes with binary data.

This formalization should do two things:

1. Don't send garbage/binary data through the REST API, which would cause a crash.
2. Show users the data encoding in the response and automatically ensure this encoding.

We could take the protobuf approach to this, making some kind of meta language for messages, for example:

TORRENTS_GET {
infohash: optional=False, encoding=base64; 
peers: optional=True, encoding=list[hex];
}

[qstokkink]

I think this has been addressed a few years ago now.