luci-base: ui.js: add LuCI.ui.menu.flushCache() function

Signed-off-by: Jo-Philipp Wich <jo@mein.io>

modules/luci-base/htdocs/luci-static/resources/ui.js

@@ -2989,6 +2989,14 @@ var UIMenu = baseclass.singleton(/** @lends LuCI.ui.menu.prototype */ {
 		return Promise.resolve(this.menu);
 	},
 
+	/**
+	 * Flush the internal menu cache to force loading a new structure on the
+	 * next page load.
+	 */
+	flushCache: function() {
+		session.setLocalData('menu', null);
+	},
+
 	/**
 	 * @param {LuCI.ui.menu.MenuNode} [node]
 	 * The menu node to retrieve the children for. Defaults to the menu's