* libnautilus-extensions/nautilus-global-preferences.c:
(global_preferences_create_dialog),
(global_preferences_get_sidebar_panel_view_identifiers),
(nautilus_global_preferences_get_enabled_sidebar_panel_view_identifiers),
(global_preferences_register_sidebar_panels_preferences_for_ui),
(global_preferences_is_sidebar_panel_enabled),
(nautilus_global_preferences_shutdown):
* libnautilus-extensions/nautilus-global-preferences.h:

Expose only a single function to deal with sidebar panels.  Return
a list of enabled view indentifiers, saving callers the work and
complication of figuring out which panels are on.

Make NAUTILUS_PREFERENCES_SIDEBAR_PANELS_NAMESPACE cause i need it
to later keep track of sidebar panel changes in NautilusWindow.

* src/ntl-uri-map.c: (got_file_info_callback),
(nautilus_navigation_info_free):
* src/ntl-uri-map.h:
* src/ntl-window-msgs.c: (nautilus_window_update_state):
Exorcise the 'sidebar_panel_identifiers' member.  Instead of
complicating life by managing this list, simply obtain it when
needed from global preferences.