Add video media to an audio-only call
The user must be able to upgrade an audio-only code to an audio/video call without the need to start a new call.
New APIs were added to allow changing the media of an ongoing call:
Manager::requestMediaChange() to request media change
Manager::answerMediaChangeRequest() to answer to a media changes request\
The media_negotiation unit test (test/unitTest/media_negotiation/media_negotiation.cpp) gives a good idea how the client and daemon should interact.