Moves part of the XMPP events which are clearly
related to the PeerConnection to RTCEvents.

Fixes an issue where the user would end up stuck in disconnected if
the video muted signalling arrived after the timeout. Also reactors
the way how the output status is figured out.

Currently if RTCPeerConnection is closed (an event is delivered) and we haven't called close method ourselves, this means browser has closed it due to suspending the PC.

Add "onmute" and "onmute" handlers to the WebRTC MediaStream and trigger
corresponding RTCEvents.

The event is triggered when the notification about the user's connection
status change arrives from the JVB.

The event is triggered when Jicofo sends 'session-terminate' and our
PeerConnection is closed.

This is an unrecoverable error and in current state of
the system reload in the client is the least complex
thing to do.

Rename variables with "stream" in name which refer to JitsiTrack.
Rename TRACK ADDED/REMOVED events.
Try to reduce direct access to remoteTracks object.
Log warning message when track is overwritten.