expose common extensions for image/movie/audio types, since python scripts had to do this internally.
- bpy.path.extensions_image
- bpy.path.extensions_movie
- bpy.path.extensions_audio

eg:

  if os.path.splitext(filename)[1].lower() in bpy.path.extensions_image:
      ... we have an image ...



git-svn-id: https://svn.blender.org/svnroot/bf-blender/trunk/blender@53547 954f8c5b-7b00-dc11-b283-0030488c597c