load subadmin.php to make sure that the hooks are connected

The "post_deleteUser" and "post_deleteGroup" hooks in lib/subadmin.php are never called because they are not connected during runtime.

To connect the hooks before the action gets triggered I added "require_once("../../lib/subadmin.php");" to some files.

I know that this is probably not the best way to make sure that the hooks are connected. So see this pull request as a starting point for discussion. I'm looking forward to hear your suggestions how to implement it in a better way.