Simple Page Sidebars

Medium risk: 3 changed templates, 1 removed hook.

• The filter plugin_locale is no longer fired. Any code hooked to it stops running silently.
• The template admin/views/edit-sidebar-screen.php changed. Any theme override of it is now out of date and will miss the change.
• The template admin/views/meta-box-page-sidebar.php changed. Any theme override of it is now out of date and will miss the change.
• The template admin/views/meta-box-sidebar-pages.php changed. Any theme override of it is now out of date and will miss the change.