Added v2.2.1 and Broadcast Multiple-Cameras demo.

Demo URI:
https://www.webrtc-experiment.com/RTCMultiConnection/Broadcast-Multiple-Cameras.html

Fixed #11

Changes Log: http://www.rtcmulticonnection.org/changes-log/#v2.0

v2.2.1 breaking updates:
--. connection.stats.sessions is removed; use
connection.sessionDescriptions instead.
--. connection.stats.numberOfSessions is removed; use
connection.numberOfSessions instead.
--. connection.stats.numberOfConnectedUsers is removed; use
connection.numberOfConnectedUsers instead.
--. connection.getStats and connection.stats are removed.