2.8 Category Admin Fix

URL changes in 2.8 was causing draggable not to work in the category admin.

So the following URL `index.php?/cp/admin_content/change_category_order?cat_id=1&group_id=1&order=up'`was getting split into `["index.php?/cp/admin_content/change_category_order?cat_id=1", "group_id=1", "order=up"]` with the issue being the the `cat_id` parameter.

This fix changes the split seperator into a regex so it accounts for both '?' and '&', which now returns `["index.php", "/cp/admin_content/change_category_order", "cat_id=4", "group_id=1", "order=up"]` fixing the issue.