Implemented a nav link generating system so that extension power what shows up in the menus rather than being hard-coded in the themes.

ext/system/main.php

@@ -0,0 +1,31 @@
+<?php
+/**
+ * Name: System
+ * Author: Matthew Barbour <matthew@darkholme.net>
+ * License: MIT
+ * Description: Provides system screen
+ */
+
+class System extends Extension
+{
+    public function onPageRequest(PageRequestEvent $event)
+    {
+        global $page, $user;
+
+        if ($event->page_matches("system")) {
+            $e = new PageSubNavBuildingEvent("system");
+            send_event($e);
+            usort($e->links, "sort_nav_links");
+            $link = $e->links[0]->link;
+
+            $page->set_redirect($link->make_link());
+            $page->set_mode(PageMode::REDIRECT);
+        }
+    }
+    public function onPageNavBuilding(PageNavBuildingEvent $event)
+    {
+        $event->add_nav_link("system", new Link('system'), "System");
+    }
+
+
+}