Multi streamers

[mcottontensor]

Adding in support for multiple streamers.

• Streamers now have IDs to identify them.
• When connecting streamers will be requested to identify using the existing 'identify' message.
• When players connect to a signalling server with only one streamer, they will be automatically subscribed to that streamer to mimic old behaviour.
• When players connect to a signalling server with multiple streamers they will be required to select a streamer to subscribe to by using the dropdown in the player configuration menu.
• Players can specify a streamer to subscribe to using the URL parameter 'StreamerId' ie. ?StreamerId=MainStreamer which will auto subscribe to MainStreamer on connect.
• Players cannot yet switch streamers mid stream and will be required to reload the browser.