Moved logout function in dedicated file

lib/php/manage.php

@@ -33,6 +33,7 @@
         <button onclick="urlinsert()">Insert new URL</button><br>
         <div id="responsetext"></div>
         <script src="<?=$GLOBALS['config']['installation_path']?>/lib/js/manage.js"></script>
+        <script src="<?=$GLOBALS['config']['installation_path']?>/lib/js/logout.js"></script>
         <script>var script_name = "<?=$GLOBALS['config']['installation_path']?>";</script>
     </body>
 </html>