Provide ability to set a menu as ajax menu. Links in an ajax menu are rendered without page load.
The render of ajax menu could be targeted to the #system-main-block, or you can set to show own block.
Active-trail, active-menu setting:
In ajax menu blocks, the core's original active-trail settings is imatated. It means, both node/add/page and ajax-menu/no_js/node/add/page the "Node add" menu item will be active, and in active-trail.
The ajaxified items (loaded into the ajax-target) get the ajax-menu-active and ajax-menu-active-trail class.