renamed participants module to users
renamed participants files to users files
changed all internal references to participants to users
fix close cam if it's not available
Merge branch 'master' of https://github.com/bigbluebutton/bigbluebutton
Merge pull request #108 from SenecaCDOT-BigBlueButton/rename-participants-module

Rename participants module
Merge remote-tracking branch 'upstream/master'