Keeping alive connections with paused video (holding muted video streams)

[emcho]

Muting video should better work by stopping video transmission because that would have a significant impact on bandwidth requirements, especially for large scale conferences.

To achieve this however we'd first need to make sure that the videobridge wouldn't expire connections without data and that it would keep them alive with ICE connectivity checks.

So for the time being this ticket lies with @lyubomir . @fippo would probably take over once we need to do the muting in JitMeet.

[emcho]

@lyubomir has almost finished this and should commit in the following day or two. Moving to February nonetheless ... because it's currently February ;)

[emcho]

This is now supported in the bridge and we can reimplement the web cam button to turn off video, rather than just black it out.