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/vehicles/hoverVehicle.h

@@ -200,6 +200,7 @@ class HoverVehicle : public Vehicle
    void advanceTime(F32 dt);
 
    DECLARE_CONOBJECT(HoverVehicle);
+   DECLARE_CATEGORY("Actor \t Controllable");
 //   static void initPersistFields();
 
    U32  packUpdate  (NetConnection *conn, U32 mask, BitStream *stream);