[PhotoFilter] simplified the code – removed unnecessary local variables
[PhotoFilter] ranamed methods
[PhotoFilter] fixed issue with audio track. replace AssetWriterInput classes with inheritance from ReadWriteSampleBufferChannel
[PhotoFilter] droped private prefix
[PhotoFilter] refactored FinishContentEditing method. Added using for quick memory freeing
[PhotoFilter] free memory
[PhotoFilter] fixed memory leak relative to UIImage.CGImage property
Merge branch 'master' of github.com:xamarin/monotouch-samples
Merge branch 'photo-filter'