Notify about the focus reason

KeyNavigation sets the focus reason always to Qt::OtherFocusReason. This
should be changed at least for tab and backtab navigation.

Change-Id: I27c654a202e2a80449dd5420460e413ca9cff75e
Reviewed-by: J-P Nurmi <jpnurmi@digia.com>
Reviewed-by: Liang Qi <liang.qi@digia.com>