Allow Gaze tracking for function pointer when hands not available.

[RangerMauve]

At the moment the code assumes there are controllers present for pointers. It'd be nice if one could attach a ray to any 3d object like the camera.

If not in the FunctionPointer class, it'd be nice if some of the core raycasting logic was exposed somewhere reusable instead.

[surreal6]

now #683 is the new PR for this feature

[Malcolmnixon]

Can you confirm the solution from surreal6 meets your needs.