Make table rows re-orderable

[Iain-S]

At the moment, table rows cannot be moved. It would be nice to be able to drag them with, for example, Jquery UI - Sortable.

Some testing would need to be done to make sure that this doesn't break the add/remove buttons.

[Iain-S]

As of 4280b22, rows can be dragged thanks to Jquery Sortable. However, it's not obvious to the user that this can be done so we probably need a symbol of some kind on each table body row.