Blender Git Loki

Changes to keying nodes:

- Replace FastGaussian blur with GaussianBokeh blur which should give better results.
- Changes a bit formula of saturation which in some cases gives better result.
Also included (commented out) original formula which was also checked by Brecht
and which gave better result in some other cases.
- Made clipping white/black temporal dependent, so hopefully it wouldn't destroy
gradients on edges.