Menu Customizer: Outline the menu-item-updating process in pseudo-code. When fields change (note that order is not handled by individual items, but depth/parents are), the original item is cloned and the cloned version is used for subsequent updates, previewing, etc. When changes are saved the cloned item is assigned to the menu and the original is deleted.

git-svn-id: https://plugins.svn.wordpress.org/menu-customizer/trunk@945753 b8457f37-d9ea-0310-8a92-e5e31aec5664