Merge remote-tracking branch 'upstream/master'

Conflicts:
	erizo_controller/erizoClient/src/Room.js
Remove unnecessary friend classes.
Some more clean-up in ExternalOutput; remove unused variables, rename some stuff for clarity, remove some unnecessary variables.  Zap some commented out code that doesn't look like it's a keeper.
Clean up whitespace/formatting.  No functional changes.
Enable opus in the SDP exchange.
Bit more clean-up.
Merge commit '2caa138' into gene_testing_3

Conflicts:
	erizo/src/erizo/SdpInfo.cpp
	erizo_controller/erizoClient/src/Room.js