Support sorting on rows

The item-view framework seems to be designed with sorting on columns only. QAbstractItemModel has only one sort() function, with no built-in support for determining whether the sorting should occur by row or column. The first parameter name for sort() is also "column".

Also, a QHeaderView using vertical orientation and showing the sort indicator, still shows the arrow vertically, instead of horizontally. One would expect that the sort indicator is painted horizontally.

It would be nice if the item-view framework supported sorting on rows.