Add info endpoint

[redfast00]

This HTTP endpoint could return the amount of connected clients per stream in JSON format. We're using mjpeg-proxy for the camera in our hackerspace, and it's nice to know if somebody is watching, that way, we can wave to them.

For example, on /api//info

{
'connections': {
  'stream1': 3,
  'stream2': 5
  }
}

I'm willing to implement this myself, but I'd first like to ask what you think of this, so I don't spend time coding a feature that you don't want in the codebase.

[kescherCode]

I think this could be a good idea, as the connections are already logged anyway to begin with (for the sake of shutting down unused streams).