N°8771 - Add Symfony form component to iTop core (#760)

- Add Symfony Form Component
- Add Symfony CSRF security component
- Add iTop default form template
- Add Twig debug extension to Twig Environment
- Add iTop abstract controller facility to get form builder
- Add Twig filter to make trans an alias of dict_s filter

lib/symfony/security-csrf/TokenStorage/ClearableTokenStorageInterface.php

@@ -0,0 +1,25 @@
+<?php
+
+/*
+ * This file is part of the Symfony package.
+ *
+ * (c) Fabien Potencier <fabien@symfony.com>
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+
+namespace Symfony\Component\Security\Csrf\TokenStorage;
+
+/**
+ * @author Christian Flothmann <christian.flothmann@sensiolabs.de>
+ */
+interface ClearableTokenStorageInterface extends TokenStorageInterface
+{
+    /**
+     * Removes all CSRF tokens.
+     *
+     * @return void
+     */
+    public function clear();
+}