Implemented the file dialog, save progress dialog, and separate thread to save
in (saving needs to be done in a separate thread so the main/GUI thread doesn't
get blocked).
OCIO config was set on a per-project basis, but we were using a singleton for
the ColorManager that would break if more than one project was ever open.
Now the ColorManager belongs to the Project and is always accessed through the
Project.
This commit adds the background functionality of the render cache invalidating
whenever a footage's color space is changed. This includes when the project's
configuration is changed as well.
itsmattkc