There were a lot of issues that arose from trying to make GUI changes
from another thread (even though we ran those functions in the right
thread). Now we store layout information until the end of the load and
make the changes then. This works much better from both a business logic
and user experience perspective.
Also prevents multiple sequences from taking focus during load and
starting a render job.
This required various changes to various parts of the infrastructure (mostly
using paths to finding the "root project" of any given object throughout).
Now theoretically infinite projects can be opened and accounted for at any
given time.
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.