lib: Add AlreadyExistsException

library/Icinga/Exception/AlreadyExistsException.php

@@ -0,0 +1,11 @@
+<?php
+/* Icinga Web 2 | (c) 2013-2015 Icinga Development Team | GPLv2+ */
+
+namespace Icinga\Exception;
+
+/**
+ * Exception thrown if something to add already exists
+ */
+class AlreadyExistsException extends IcingaException
+{
+}