The top module creates toplevel windows in the application and manages
things like their saved settings (preferences) and their relationship with
other toplevel windows.

Switches:

    tag
	This is the name by which you will refer to the currently active
	instance of this toplevel.

    title
	Specify a title to use when iconifying the window.

    parent
        Specify a window name as the parent.  When the parent is destroyed,
        this toplevel will die too.
        
    main
	This toplevel is a main window.  When the last of its kind dies,
	the application should exit.  The default is false, so for main
	windows, you should specify "-main 1".
        
    build
	Specify a script to execute in order to populate the toplevel
	with widgets.  This is done so future clones of the toplevel can
	be built later when wanted by the user.

    module
	Specify a name of a module to associate preferences with.  This
	defaults to the name of the current application.

    close
	Specify a script to execute each time the toplevel is closed.
	
    menu
	If true, a menubar will be included at the top of the window.

    restore
	If true, preferences will be saved and restored for this toplevel.

Widget commands:

    pane
	Send the following commands to the named pane as in the example: 
	"m pane mydbe cget"
	
	Note, this can be omitted as long as the name (tag) of the pane
	is unique among other possible choices at this syntactical point.
    
    menu
	Send the following commands to the menu bar.

    geom
	Execute "wm geometry $w $args" on the toplevel.

    pref
	Get or set preferences (normally used internally).

    close
	Destroy this toplevel window in an orderly way (includes saving
	preferences.)
    
    tag
	Return the tag of the named toplevel window.
