AvInputAudio: fix audio demux offset
Merge pull request #102 from valnoel/master

Fix audio demux
Merge branch 'master' of https://github.com/avTranscoder/avTranscoder into dev_clean_refactoring
EssenceTransform: rename folder/files/classes whithout 'essence'

* Rename folder 'essenceTransform' to 'transform'.
* Rename files to ITransform, VideoTransform and AudioTransform.
* Rename classes to ITransform, VideoTransform and AudioTransform.
* No sense to have transforms for coded data. So transforms are
implicitly for essence (decoded) data.
essenceStructures: rename folder to frame

The folder contains all classes about frame.
Remove DataStream class

* Duplicate with Frame class.
* Add a typedef of Frame, CodedData, to represent buffer of coded data.
AvInputStream: has ownership to a single codec

* In constructor, instanciate a videoCodec, or an AudioCodec, or a
DataCodec.
* Get the codec with getter (use reference).
AvInputStream: clean

* Indentation.
* Implement constructor per copy in cpp.