Add intersection for BoundingSphere

Added support for detecting intersection between the ray and the
bounding sphere. It is determined automatically by whether the
BaseObject3D object has a bounding sphere. If it does not, it reverts to
detecting intersection with the bounding box.
Merge branch 'master' of https://github.com/MasDennis/Rajawali
Added Intersector utility class

Added Intersector utility class with code adapted from libGDX. Currently
supports ray-sphere, ray-triangle, and ray-plane intersection detection.
Updated RayPickingVisitor to use Intersector

Moved ray-sphere intersection code out to Intersector utility class.
Fixed thread synchronization issues

Fixed thread synchronization issues with the static method calls when
using Number3D instances as arguments which caused GLThread to slow down
dramatically and blank in and out when the method is called.
Merge pull request #437 from AndrewJo/master

Detection for intersection between the RayPickingVisitor and BoundingSphere