Implement XMPP health check

Initial implementation of /check-health endpoint

POST a JSON like so:

{
    "reqType": "ws",
    "host": "some.host",
    "port": 7070
}

and it'll verify if it's reachable.  Further iterations will check for
protocol (XMPP, websocket, XMPP over websocket), and try initiating a
stream.

Maintain remote and local streams separately

Initial working prototype

The websocket stream opens!  Still need to figure out why subsequent
packets don't get sent.

Rewrite as websockets

Change 'wsabi' dir to 'wsabipkg'

Init