By ensuring that the current index follows the focus of an index widget,
we can ensure that moving the cursor will happen in the way that is
expected from the focused widget.
Task-number: QTBUG-27793
Change-Id: Ia36891a94ce41c7d12fba678de23a6f3b69374ae
Reviewed-by: Richard Moe Gustavsen <richard.gustavsen@qt.io>
Reviewed-by: Christian Ehrlicher <ch.ehrlicher@gmx.de>