Menu selection handling

• There is no method handleEvent() for MenuComponent or its subclasses
• There is no method action() for MenuComponent or its subclasses
• Events and actions are handled by the Frame container of the MenuComponent.
• The default action() for Frame does nothing and returns false.
• The action() method must be overridden to handle menu actions. (Overriding handleAction() is not so good since it dispatches other events as well.)