added an extension system

src/Silex/Application.php

@@ -68,6 +68,15 @@ class Application extends \Pimple implements HttpKernelInterface, EventSubscribe
         });
     }
 
+    public function register(ExtensionInterface $extension, array $values)
+    {
+        foreach ($values as $key => $value) {
+            $this[$key] = $value;
+        }
+
+        $extension->register($this);
+    }
+
     /**
      * Maps a pattern to a callable.
      *

src/Silex/ExtensionInterface.php

+<?php
+
+/*
+ * This file is part of the Silex framework.
+ *
+ * (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 Silex;
+
+interface ExtensionInterface
+{
+    function register(Application $app);
+}