Add VisualModel to SceneObject
The current scene object implementation is causing too much data to be placed in the Geometry class. For instance, RenderMaterial and visibility functions should be moved out of the Geometry class. Currently, each SceneObject can only contain one visual geometry object. In order to overcome this, we proposed that each scene object can contain a vector of the new VisualModel class. Each VisualModel can contain a RenderMaterial and Geometry object.