Wire the interface get/setPanelMode as part of the expected interface
for panels defined by the user interface.  The basic interface provided
by the CFJPanel just provides an object attribute and accessors as an
implementation.  The application panels need to override that basic
implementation with code that reacts to changes in the attribute value.

The window implementations deriving from CFJInternalFrame will also provide
implementations of the panel interface, overloading the getters and setters
for their PanelMode attributes to react by propagating any changes to the
PanelMode to their component CFJPanels which define the user interface.

SETTER AttrJPanel.setPanelMode( PanelMode value )