Introduce interface SortRules

refs #6644

library/Icinga/Data/SortRules.php

@@ -0,0 +1,14 @@
+<?php
+/* Icinga Web 2 | (c) 2013-2015 Icinga Development Team | GPLv2+ */
+
+namespace Icinga\Data;
+
+interface SortRules
+{
+    /**
+     * Return some sort rules
+     *
+     * @return  array
+     */
+    public function getSortRules();
+}