AVFoundation: Use CoreAnimation to render video to QVideoWidget

AVFoundation: Use CoreAnimation to render video to QVideoWidget

Previously a QGLWidget was used as a target for the
AVFVideoFrameRenderer.  This was uncessary as it is possible to render
directly on top of the QWidget using the CoreAnimation Framework.

Change-Id: I08923c85fd56c8874c1d8c187ae5145e220fab92
Reviewed-by: Richard Moe Gustavsen <richard.gustavsen@digia.com>