blender scene should be able to remember OCIO setup.

In our studio, we are working on many projects at the same time. Some use aces1.0.3, some use 1.2, some just don't use aces.

Currently only way to set aces is using OCIO variable when you open a scene. But then the ocio config path is fixed inside the window. If an artist works another scene from the window, things could be messed.

Open another scene from scratch should be fine. But artists could open any scene inside already opened window by mistake. Force not to use open menu is also unnatural.

The scene should be able to remember ocio path, if set, as like nuke.