Transcoder: add a stream from a StreamTranscoder
StreamTranscoder: fix setProfile of dummy video stream

Get the ImageDesc from the
_inputEssence when we set the outputVideo stream.
DummyVideo: add setFrame

* Can create a dummyVideo, and set its Frame.
* When read the next frame of the object, read silent(black) if no
specific Frame was set, or read the data of the Frame specified.
Merge branch 'dev_OptionLoader' into dev_Dummy
Merge branch 'master' of https://github.com/avTranscoder/avTranscoder into dev_Dummy
Merge pull request #27 from cchampet/dev_Dummy

Dummy Video