Add sort direction icon for variant options table

[bjarnef]

I think it would be great to add a sort direction icon for ascending/descending like in listview instead of icon-navigation-road - so it will be more clear than sorting in happening, e.g. if sorting on a column with same values.

[rasmusfjord]

I would agree, an option to drag in the variant table instead of just an asc/desc would be nice aswell!