Deoldify Vapoursynth filter

[Dan64]

With the new dev version, the problem regarding the ddcolor model has been solved.
The fix introduced regarding the conversion to RGB24 when input is GRAY8 caused a lot of problems on other filters.
For example selecting Tewak to de-saturate an image to B&W before ddeoldify is not more working.

Please revert the code back. I'm will apply the transformation to RGB24 directly in the filter if necessary.
I'm doing so many colorspace conversion in the filter that one more will not create any problem.

Thanks,
Dan

P.S.
I will release a new version with the patch.