feat(ajax): adds elgg/Ajax#forward method

Adds a new method to elgg/Ajax AMD module that allows a redirect
to a new page while keeping the spinner running

docs/guides/ajax.rst

@@ -249,6 +249,17 @@ Notes for forms:
 	In ajax views and forms, note that ``$vars`` can be populated by client input. The data is filtered like
 	``get_input()``, but may not be the type you're expecting or may have unexpected keys.
 
+Redirects
+---------
+
+Use ``ajax.forward()`` to start a spinner and redirect the user to a new destination.
+
+.. code-block:: js
+
+    var Ajax = require('elgg/Ajax');
+    var ajax = new Ajax();
+	ajax.forward('/activity');
+
 
 Piggybacking on an Ajax request
 -------------------------------

views/default/elgg/Ajax.js

@@ -351,6 +351,18 @@ define(function (require) {
 
 			return new FormData($(el)[0]);
 		};
+
+		/**
+		 * Issue a redirect and display a spinner
+		 *
+		 * @param destination String URL to forward to
+		 * @returns {void}
+		 */
+		this.forward = function(destination) {
+			spinner_starts++;
+			spinner.start();
+			elgg.forward(destination);
+		};
 	}
 
 	/**

views/default/forms/login.js

@@ -4,33 +4,30 @@ define(function(require) {
 	var Ajax = require('elgg/Ajax');
 	var spinner = require('elgg/spinner');
 
-	// manage Spinner manually
-	var ajax = new Ajax(false);
-
 	$(document).on('submit', '.elgg-form-login', function(e) {
 		var $form = $(this);
 
-		spinner.start();
+		var ajax = new Ajax();
+
 		ajax.action($form.prop('action'), {
 			data: ajax.objectify($form)
 		}).done(function(json, status, jqXHR) {
-			if (jqXHR.AjaxData.status == -1) {
+			if (jqXHR.AjaxData.status === -1) {
 				$('input[name=password]', $form).val('').focus();
-				spinner.stop();
 				return;
 			}
 
 			if (json) {
 				if (typeof json.forward === 'string') {
-					elgg.forward(json.forward);
+					ajax.forward(json.forward);
 					return;
 				} else if (json.forward === -1) {
-					elgg.forward(location.href);
+					ajax.forward(location.href);
 					return;
 				}
 			}
 
-			elgg.forward();
+			ajax.forward();
 		});
 
 		e.preventDefault();