Text: new form element type, catch type issues

fixes #1200

library/Director/Web/Form/Element/Text.php

@@ -0,0 +1,16 @@
+<?php
+
+namespace Icinga\Module\Director\Web\Form\Element;
+
+use Zend_Form_Element_Text as ZfText;
+
+class Text extends ZfText
+{
+    public function setValue($value)
+    {
+        if (\is_array($value)) {
+            $value = \json_encode($value);
+        }
+        return parent::setValue((string) $value);
+    }
+}