Little reminder for the GraspIt main classes inheritance structure and references between objects.

World: Pointer to IVMgr.
IVMgr: inherits QWidget.
       Created in GraspItGUI.
       Pointer to world and all the inventor files, and the viewer.
WorldElement: inherits QObject.
       Pointer to world and inventor objects.
Robot: inherits from WorldElement.
       Pointer to World (because WorldElement).
Hand:  inherited from Robot.
Body:  inherits WorldElement.
       Pointers to inventor objects.
