DatasStructures: split in CodedStructures and EssenceStructures
Image / ImageDesc: rename to VideoFrame / VideoFrameDesc
EssenceDesc: rename to CodedDesc
Clean includes

* Remove unused includes.
* Use fast forward declaration if possible.
Merge branch 'master' of https://github.com/avTranscoder/avTranscoder into dev_refactoringStructures
clean includes: reorder some includes
Merge pull request #29 from cchampet/dev_refactoringStructures

Refactoring & clean