clean up "Add" menubar categoes on the 3d object side via the following:

SceneObject now defaults to a category of "misc"
getCategoryOfClass now checks parent classes for what categories they hold so that variants can inherit
categories are in one of a few rough groups and subgroups depending on actual mapper needs/usages

Engine/source/T3D/pathCamera.h

@@ -92,6 +92,7 @@ private:
 
 public:
    DECLARE_CONOBJECT(PathCamera);
+   DECLARE_CATEGORY("Cinematic");
    
    DECLARE_CALLBACK( void, onNode, (S32 node));