Restrict bezier pointer height when controller is at an angle

[thestonefox]

At the moment you can set the bezier pointer height to a finite length, which prevents the pointer from reaching the ground, however the forward beam can still reach the ground which kind of defeats the purpose.

[thestonefox]

Some how need to limit the forward beam distance of the bezier beam based on the rotation of the controller to be relative to the height of the downward beam.

[thestonefox]

This issue persists in V4 https://github.com/ExtendRealityLtd/VRTK.Unity.Core/issues/89