ENH: Simplifies scene object class hierarchy

1. Merge CollidingSceneObject into SceneObject. SceneObject is now optionally viewable
and collideable but not movable. SceneObject class has all the functionality of a static object.
2. Rename imstkLigUtility to imstkLogger
3. Rename virtualCouplingObject to virtualToolObject
4. Consistency with brackets for imstk namespace
5. Move enums that  into imstk scope unless if the enum has no meaning outside the class