image open.
	
* app/widgets/gimpdialogfactory.[ch]: Add 'toggle_visibility' to
GimpDialogFactory and as a parameter to gimp_dialog_factory_new(),
and set it there.

(gimp_dialog_factories_hide_foreach): Don't hide dialogs belonging
to factories with toggle_visibility FALSE.

* app/display/gimpdisplayshell-callbacks.c
(gimp_display_shell_canvas_tool_events): Move no-image event
handling to a new helper function, and make pressing Tab hide
windows.

* app/dialogs/dialogs.c (dialogs_init): Allow toggling visibility
for all factories except the display-factory.

svn path=/trunk/; revision=27077