still working on improving the global audio code quality, trying to make it work properly, not there yet; we're probably going to create a new CallAgent for the user who listens to the global audio, because the implementation is still not straightforward
looks like it's working fine now, still need more testing with a large number of users; also GLOBAL_AUDIO_7* shouldn't appear in the users window
Merge branch 'merging-global-audio' of github.com:mconf/bigbluebutton into merge-global-audio
 - filter out global audio user so we won't display it on the user's list
 - cleanup