Deoldify Vapoursynth filter

[Dan64]

Hello Selur,

  I completed the ColorMNet implementation.
  Please find attached the last version RC18 (I hope).
  The main changes are:

1. now there are only 2 encode modes for ColorMNet: (0) remote, (1) local
   
2. removed the Future Warnings
   
3. improved the explanation of ColorMNet parameters
   
4. RefMerge and related parameters (Weight, Threshold) are implemented only for Deep-Exemplar
   
5. The parameter Preset (fast, medium, slow) will apply also to ColorMNet 
   

  On my PC, with Preset "medium", the speed of ColorMNet[remote] (8.2 fps) is near to Deep-Exemplar (8.6 fps).
  Unfortunately, while ColorMNet improved the temporal consistency, the long memory is introducing significant color artifacts in smooth scene change.
  For this reason I kept the encode method (1) local that is able to manage small memory frames. But in this case I think that Deep-Exemplar is better.
  In summary to get a good coloring results are necessary both the models: ColorMNet and Deep-Exemplar.

  Now I will start to work to improve the scene change implementation, which can affect the output quality when HAVC is used with the Exemplar-based models.

Thanks,
Dan