Menu Customizer:

- Rename nav_menus[id][controls] to nav_menu_id. This control is really the primary thing that controls the contents and order of nav menus, so it deserves a name that implies its purpose better.
- Bypass the mess that is `wp_update_nav_menu_item()` when saving menus, where only a couple of menu item fields need to be changed.
- Temporarily prevent all added menu items from being hidden via the new Customizer control `active` functions (need to figure out why they're always hidden with @westonruter).


git-svn-id: https://plugins.svn.wordpress.org/menu-customizer/trunk@947574 b8457f37-d9ea-0310-8a92-e5e31aec5664