Add better maintenance handling

lib/classes/API/V1/exception/maintenance.php

@@ -0,0 +1,21 @@
+<?php
+
+/*
+ * This file is part of Phraseanet
+ *
+ * (c) 2005-2013 Alchemy
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+
+/**
+ *
+ * @package     APIv1
+ * @license     http://opensource.org/licenses/gpl-3.0 GPLv3
+ * @link        www.phraseanet.com
+ */
+class API_V1_exception_maintenance extends API_V1_exception_abstract
+{
+    protected static $details = 'Server is offline for maintenance, try again soon.';
+}