Implement Websockets backend as alternative to some Flask endpoints

[tgoodyear]

For the real-time charting associated with the management dashboard, websockets may be more appropriate than constantly polling the RPC server. This would allow STINGER to push updates directly to a connected client.

Reference: http://www.fullstackpython.com/websockets.html

[davidediger]

That would be good. I believe our version of the Mongoose web server also supports Websockets. I tried to do a small proof-of-concept some time ago, but never quite got it to work. Seems very appropriate for health and status monitoring.