You can get the list of pixel formats and sample formats without an
instance of OptionLoader.

Conflicts:

	src/AvTranscoder/OptionLoader.cpp
	src/AvTranscoder/OptionLoader.hpp

OutputVideo and OutputAudio: raise runtime_error if "could not allocate"
or "could not open" video / audio codec.

Fix: the channel layout is not required by FFMPEG when open audio codec context. So an audio profile has not to set this value.

Conflicts:
	src/AvTranscoder/Transcoder/StreamTranscoder.cpp
	src/AvTranscoder/Transcoder/StreamTranscoder.hpp

…scoder into cchampet-dev_OptionLoader

Conflicts:
	src/AvTranscoder/EssenceStream/OutputVideo.cpp
	src/AvTranscoder/OptionLoader.cpp