AVWriter: an audio stream is not silent by default
AVWriter: delete audioSelectChannel and audiChannelIndex OFX parameters

* These parameters do not have use cas in real life.
* There is a lot to do before think about extract a substream...
AVWriter: delete metadataEncoder OFX parameter

This parameter corresponds to the name/settings of the software/hardware
that produced the file. It was automatically overwrite by FFmpeg /
libav.
AVWriter: by default number of audio stream is one

* No effect if the stream is not silent and there is no file name
selected.
* The parameter is set to one to give a visibility of the audio
parameters to the user.
AVWriter: delete changeEncoding OFX parameter

* By default the plugin transcode audio streams.
* Comment the rewrap case: this will be manage by a new choice in the
list of "encodage".
AVVWriterFactory: update name and help of OFX audio parameters

* Fit to TuttleOFX nomenclature: upper case at the beginning of each
word.
* Explain new vocabulary (help to audioNbStream parameter).
AVWriter: fix number of audio streams of input audio files

* Input files given to audio parameters could have not only audio
stream.
* Get number of audio streams instead of number of streams.
AVWriter: add rewrap case in list of 'output encoding'

* The rewrap case is available in the list of preset of the audio
'Output'.
* Warning: need to hide the offset when rewrap is selected.
AVWriter: hide audio offset when rewrap
AVWriterPlugin: refactoring update functions of audio OFX parameters

No need to loop on each audio parameters at each update.
AVWriterPlugin: refactoring

* Simplify call of substr.
* UpdateAudioSilent: reorder instructions.
AudioVideo: display name and label for OFX Choice parameters

* In order to give more details to the users, for each OFX Choice
parameters we display the name and the label (correspond to the help for
parameters from FFmpeg options).
AVWriterPlugin: update range of index audio stream OFX parameter

* Update dynamically the range depending on the number of audio streams
in the input file indicated.
AVWriter: add OFX parameter to display audio info of input file indicated

* Add a String (multilines) OFX parameter for each audio 'Output'.
* Display the number of audio streams, and the number of channels for
each stream.
AVWriter: refactoring

* Rename maxNbAudioStream to maxNbAudioOutput.
* When instanciate the plugin, by default hide and disable all OFX audio
parameters.
AVWriter: audio offset OFX parameter in milliseconds

* The parameter was in frames.
* Update its hint and range.