Fix broken variable

Handles the case where we can receive the presence with the video type before we have received and created the remote track.

Fixes a problem where, sending that namespace on every presence will make the server think we are joining every time and will return us the message history for the muc.

If in the presence there is 110 and 307 status codes there was an error in processing. When kicked the other participants were not cleared from the conference. Firing an event for focus leaving the conference when we are kicked.

via presence (via special items with a tag name beginning with
"jitsi_participant_). An events is fired when the value of a property changes.

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.