SpecialController: allow to link special pages

fixes #39

application/controllers/SpecialController.php

@@ -0,0 +1,27 @@
+<?php
+
+namespace Icinga\Module\Pnp\Controllers;
+
+use Icinga\Module\Pnp\Web\Controller;
+
+class SpecialController extends Controller
+{
+    public function indexAction()
+    {
+        $url = $this->getRequest()->getUrl();
+        $queryString = $url->getQueryString();
+
+        $this->view->url = \sprintf(
+            '%s/special?%s',
+            $this->getBaseUrl(),
+            $queryString
+        );
+
+        $this->getTabs()->add('special', [
+            'label' => $this->translate('Special'),
+            'url'   => $url,
+        ])->activate('special');
+
+        $this->setViewScript('index/iframe');
+    }
+}