Blender Git Loki

Fixes for proxies color space

Basically proxy colorspace didn't work well enough.

It is still a bit weird and mainly:

- Proxies for image sequences are built in the image color space.

- Proxies for movies are built in the movie color space.

This could be unified but would need some work in proxy build
to make it not just pipe frames from one FFmpeg context to
another but also apply OCIO on it.