Store the "show extra icons" flag in a cookie in addition to the global/default setting. This way each user can have their own preference, and we don't need to send an AJAX request each time the user clicks More/Less.

git-svn-id: https://plugins.svn.wordpress.org/admin-menu-editor/trunk@872635 b8457f37-d9ea-0310-8a92-e5e31aec5664