WebRTC server support (publishing and watching)

[KallDrexx]

Workflow steps should be created that allow either ingesting media via WebRTC or connecting via WebRTC to watch a stream.

• [x] - Publisher connection handler
• [x] - Watcher connection handler
• [x] - Endpoint
• [x] - Endpoint validator
• [x] - HTTP handler for receiving offers
• [x] - webrtc_receive workflow step
• [ ] - webrtc_watch workflow step
• [ ] - End to end validation