Calculate display order for imported resume items.
We do this by looking for whether the items are connected to one of the special Mahara groupings. If they are, we read the display order and use it - otherwise, the display order isn't used, as we assume the display order is for some other selection that is irrelevant to Mahara. This assumption might need to change in future. Signed-off-by: Nigel McNie <email@example.com>