Fix button focus issues

This change introduces derived classes for ComboButton, DropDownButton
and Select that make sure that buttons do not remain focused after their
menus are closed. This allows using hotkeys after closing them.

js/form/DropDownButton.js

@@ -0,0 +1,12 @@
+/* global dijit */
+define(["dojo/_base/declare", "dijit/form/DropDownButton"], function (declare) {
+	return declare("fox.form.DropDownButton", dijit.form.DropDownButton, {
+		startup: function() {
+			this.inherited(arguments);
+			this.dropDown.autoFocus = true; // Allow dropdown menu to be focused on click
+		},
+		focus: function() {
+			return; // Stop dijit.form.DropDownButton from keeping focus after closing the menu
+		},
+	});
+});