OpenColorIO Config Management

Blender's current color management approach has a few shortcomings.

1. A lot of artists replace Blender's default OCIO config with something else. They might need proprietary transformations for their specific camera, a custom view transform (flim, GT7, etc.), and so on. This replacement requires manually tinkering with files and directories.

2. One might need to use different configs for different projects, so they end up having to re-tinker with files and directories every time they switch between their projects.

3. Sharing a project that uses a custom config becomes quite the headache! You need to teach the other person how to do the tinkering with files and directories.

4. Sometimes we want to use a color space from config A and a view transform from config B, so we need to manually edit the .ocio files to make something custom.

Because of this, I believe the following features are necessary and not just quality-of-life improvements.

1. Allow the user to add one or more custom OCIO configs in Preferences. These will be available globally for the entire Blender installation.

2. Color space combo lists show color spaces from all added configs plus the default built-in config.

3. View transform and display combo lists show view transforms from all added configs plus the default built-in config.

4. A checkbox lets us embed our custom configs directly into the .blend file so sharing becomes straightforward. Of course, it only embeds the ones that were actually referenced in the current project.