Screw fixed, collision shape adjustments

* extensionsRequired was fixed to require the physics extensions.
* Combine for the balls was set to Maximum. Can't see the difference between the modes though, just shooting in the dark here.
* Archimedes screw now rotates properly: unparented from the root Compound parent, set to Infinite Mass, and Angular Velocity was set to negative.
* Vertex positions were edited on physics shapes at top and bottom of elevator shaft, to prevent the balls from getting stuck there.
* Bottom gravity trigger for Interactivity extension was repositioned so ball gets to the center of the elevator shaft before it enters the trigger.
* Tried enabling tangents on export, but that caused more validation problems than without it, because the exporter seems to add tangents to ALL meshes, regardless of whether they have a normal map or not. So, tangent export was deactivated.

Author: echadwick-artist