Renamed RectangularPaddle back to ScintillatorPaddle, then created a new RectangularPaddle from which ScintillatorPaddle is now subtyped. This was to preserve the prexisting API. Modified the BSTFactory to construct the BST in a more precise manner. Implemented Arc3D and ArcSurface3D. ArcSurface3D has working line intersection functions. Added useful functions to Point3D and Vector3D.