* libnautilus-extensions/nautilus-global-preferences.c:
(global_preferences_create_dialog),
(global_preferences_close_dialog_callback),
(nautilus_global_preferences_show_dialog),
(nautilus_global_preferences_hide_dialog),
(nautilus_global_preferences_set_dialog_title):
* libnautilus-extensions/nautilus-global-preferences.h:
Add functions for hiding the preferences dialog and changing its
title.  Also, connect a "closed" signal to prevent the dialog from
killing itself since its singleton and lives for the entire life
of the application.

* nautilus-widgets/nautilus-user-level-manager.c:
(nautilus_user_level_manager_get_user_level),
(nautilus_user_level_manager_make_current_gconf_key),
(nautilus_user_level_manager_get_user_level_string):
* nautilus-widgets/nautilus-user-level-manager.h:
Make nautilus_user_level_manager_get_user_level_string () public.

* src/nautilus-window-menus.c: (settings_menu_customize_callback),
(nautilus_window_initialize_menus), (user_level_changed_callback),
(update_user_level_menu_items), (get_customize_user_level_string),
(get_customize_user_level_setttings_menu_string):
Change the customize menu item's label based on the user level.
Make it insensitive for the novice user level.  Close the
preferences dialog when the user level changes to novice.