Separate V4L1 from V4L2.

It adds V4l1Device and V4l2Device. They both inherit from VideoDevice.
It now uses enumeration of supported frame sizes for V4L2.
As some driver still don't support that, I wiil add a way to make it work anyway.

The storage of all VideoDevice's uses now pointers to VideoDevice as we want late binding on V4l1Device and V4l2Device instead of early binding on VideoDevice.

The use of pixel_format and standard enum made no sense, it now uses V4L and V4L2 enums which are as good as the old ones in VideoDevice.

Switched pixelformat storage with unsigned int instead of int, it considerably decreases the number of warnings at compile time.