Set global timeout for Ajax operations

`ajaxSetup()` sets the default values for future Ajax operations.

See also
https://api.jquery.com/jQuery.ajaxSetup/
https://api.jquery.com/jquery.ajax/

Signed-off-by: David Mehren <git@herrmehren.de>

public/js/index.js

@@ -621,6 +621,11 @@ Visibility.change(function (e, state) {
 
 // when page ready
 $(document).ready(function () {
+  // set global ajax timeout
+  $.ajaxSetup({
+    timeout: 10000
+  })
+
   idle.checkAway()
   checkResponsive()
   // if in smaller screen, we don't need advanced scrollbar