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

The previous method was clobbering the JingleSession prototype,
preventing the creation of additional subclasses.

Jicofo is smart and can find any bridge with service discovery and/or
pubsub.

Since (1) half of the disco uses check whether the feature in question
is supported, (2) the other half appears to not absolutely require
disco, and (3) disco needs to be explicitly included/required in order
to be supported, make disco completely optional.

The function filter_special_chars does not have to throw a TypeError
when its argument text is null or undefined because (1) it can be argued
that neither of these two contains special characters and (2) it is much
more convenient to have the check in the function in question rather at
its multiple call sites.

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.