-Added new primitives for material preview: cube, suzanne, plane, "hair" geometry.
-Fixed incorrect motion blur evaluation: shutter close / open was only being taken into account for camera motion blur.
-Change: appleseed.studio should launch without needing to communicate with Blender, as this hangs Blender until appleseed.studio is quit. But Blender seems to hang anyway, this may be an internal bug.
-Deleted .bak, .pyd, .pyc cache files from repository
-Temporarily set --message-verbosity to "fatal", since feedback was cluttering console.  Need to add a UI enum for message verbosity levels.