Merged the latest version 2.11 changes
Copy all content elements if pages are duplicated with childs (see #5241)
The table sorter did not work if jQuery and MooTools were active (see #5228)
Handle the case that `glob()` returns `false` (see #5226)
Added the missing `UserGroupModel` class (see #5218)
Show the "edit header" button even if it is disabled