Profile: can loadProfiles with the constructor

By default the list of profiles is not loaded.
Profile: implement getAudioProfiles
Profile: add update function

The function updates the corresponding profile, or create a new one if
it doesn't exist.
Transcoder: can add a stream with a custum profile

* Transcoder: 3 ways to add a stream, which call the private function
add( const InputStreamDesc& streamDefinition ).
* This impacts:
     * StreamTranscoder: init with a ProfileDesc instead of a
profileName.
     * OutputEssence (and the subclasses OutputVideo and OutputAudio):
set profile with a ProfileDesc instead of a profileName.
     * swig avTranscoder.i: include Profile because of includes in
output essence source files.
     * avTranscoder app.: can't update the profile with only the
profileName.
     * optionChecker app.: set the profile with the profileDesc.
Profile: add comment
Merge pull request #11 from cchampet/master

Transcoder: can add a stream with a custum profile