Remove AVAsset category

Now is in a gist https://gist.github.com/lukabernardi/5020724, in the future I will eventually move this in a separate project

Signed-off-by: Luca Bernardi <luka.bernardi@gmail.com>
Move RadiansToDegree in a more appropriate place

Signed-off-by: Luca Bernardi <luka.bernardi@gmail.com>