Create a menu-opener featured link in the menu builder

[dswebsme]

With this commit we've successfully decoupled the menu-opener from the right-menu.

9f4c200

This allows us to manipulate the placement of the menu-opener via hooks. For example, a child theme could contain:

remove_action( 'emma_after_right_menu_items', 'emma_add_menu_opener_menu_item' );
add_action( 'emma_after_primary_menu_items', 'emma_add_menu_opener_menu_item' );

Unfortunately, there are still some limitations to this approach in that we can still only place the menu-opener in one of the 4 default menu areas (left, right, primary, footer). We could not use this method to add a the menu-opener to a utility-widget area.

Ideally, we should be able to place the menu-opener freely and without code in any menu as a Featured Link in the WordPress menu builder.

This would also allow us to revert these commits to keep our menu areas clean and consistent with the WordPress way:

• e9e75a5
• a85d051
• f9f0c15
• Similarly, the right-menu could also be restored to it's former state (prior to the menu rework)