Deoldify Vapoursynth filter

[Dan64]

I like the new GUI   
I will test it to see if everything is Ok.

Regarding the parameters ref_weight, ref_thresh they were already available in the release 4.0.0: __init__.py
But has been added to handle very specific situations and it is right that are not included in the GUI.

I changed HAVC_main() to include also the parameter DeepExModel (see attached RC3) so that it will be possible to select the Exemplar based model to use for colors propagation.

Thanks,
Dan