The two `VIRTVAR`s for Orientation in subsystems and submodel instances do the same thing, but did not have the same code - in particular, the subsystem version did not update the subsystem angle and turret angle. This syncs them up.
Allow scripts to reference submodels, submodel instances, and model instances. Currently just a few properties (like Orientation and Radius) can be accessed, but this can be easily expanded in the future.
Also add relevant functions to calculate real-world positions and orientations of rotated submodels.