Refactor MIDI & Audio contexts for demo use case

[obensource]

Refactor existing WebMIDI/Audio functionality to represent intended Remote-Performer use case:

• Web Audio contexts in each client used for testing purposes–to standard audio output.
• MIDI contexts send message output to specified port, hooked by peer-server (peer.js WebRTC server)
• MIDI contexts receiving input from optional:
  • Standard interface input
  • Specified port
• Expose MIDI port via Ableton Max/MSP(Max for Live) for performance data stream.