Provide discovery-swarm over WS

[RangerMauve]

I think the gateway would be way more useful (and potentially more private) if instead of provoding WS for replicating a hyperdrive, it provided a WS interface to discovery-swarm.

I'm thinking this should be built as a separate module first.

• It shouldn't reveal peer IP addresses
• It should work over a stream.
• All peer connections should be multiplexed over the single stream
• Have the constructor take a discovery-swarm instance and return a handleStream(stream) listener. (or something like that)
• It should use protocol buffers for an RPC API
  • join(discoveryKey) -> To the gateway
  • leave(discoveryKey) -> To the gateway
  • peer(discoveryKey, peerId) -> From the gateway
  • connect(peerId, streamId) -> To the gateway
  • disconnect(peerId, streamId) -> To the gateway
  • data(peerId, streamId, data) -> Either way

The client-side should take a stream as an argument and expose the same API as discovery-swarm