Add a standalone AjaxView

Having a self-contained view class will allow debugkit to continue
working even when the application doesn't have an AjaxView, or when that
AjaxView is not suitable for rendering debugkit.

Refs #416

src/Controller/PanelsController.php

@@ -53,7 +53,9 @@ public function beforeFilter(Event $event)
      */
     public function beforeRender(Event $event)
     {
-        $this->viewBuilder()->layout('DebugKit.panel')->className('View');
+        $this->viewBuilder()
+            ->layout('DebugKit.panel')
+            ->className('DebugKit.Ajax');
     }
 
     /**
@@ -87,6 +89,7 @@ public function view($id = null)
         $this->Cookie->configKey('debugKit_sort', 'encryption', false);
         $this->set('sort', $this->Cookie->read('debugKit_sort'));
         $panel = $this->Panels->get($id);
+
         $this->set('panel', $panel);
         $this->set(unserialize($panel->content));
     }

src/Controller/RequestsController.php

@@ -48,7 +48,9 @@ public function beforeFilter(Event $event)
      */
     public function beforeRender(Event $event)
     {
-        $this->viewBuilder()->layout('DebugKit.toolbar')->className('View');
+        $this->viewBuilder()
+            ->layout('DebugKit.toolbar')
+            ->className('DebugKit.Ajax');
     }
 
     /**

src/View/AjaxView.php

@@ -0,0 +1,36 @@
+<?php
+/**
+ * CakePHP(tm) : Rapid Development Framework (http://cakephp.org)
+ * Copyright (c) Cake Software Foundation, Inc. (http://cakefoundation.org)
+ *
+ * Licensed under The MIT License
+ * For full copyright and license information, please see the LICENSE.txt
+ * Redistributions of files must retain the above copyright notice.
+ *
+ * @copyright     Copyright (c) Cake Software Foundation, Inc. (http://cakefoundation.org)
+ * @link          http://cakephp.org CakePHP(tm) Project
+ * @since         3.2.8
+ * @license       http://www.opensource.org/licenses/mit-license.php MIT License
+ */
+namespace DebugKit\View;
+
+use Cake\View\View;
+
+/**
+ * A view class that is used for AJAX responses.
+ * Currently only switches the default layout and sets the response type -
+ * which just maps to text/html by default.
+ */
+class AjaxView extends View
+{
+    /**
+     * Initialization hook method.
+     *
+     * @return void
+     */
+    public function initialize()
+    {
+        parent::initialize();
+        $this->response->type('ajax');
+    }
+}