- implemented a native Cocoa-OpenGL screen
- introduced CVLayer to be used as "binding class"
within all native-cocoa layers
- runloop is now ruled by the Screen which will call
Context::cafudda() only when the DisplayLink asks for
a new videoframe to render
- both CVideoFile and CVideoGrabber are now working properly
(effects are not available yet on the CVideoGrabber layer
but I'm going to extend filtering functionalities to
the videograbber asap)
