OutlineViews: Make behavior consistent with other views

Allow them to be focused, activate also on return/enter. Also fix focus
handling so that assigning a shortcut to "Activate Outline View"
actually
works.

Change-Id: I878777ae0dad493af1715b36ee264a4f0c12443e
Reviewed-by: Eike Ziller <eike.ziller@digia.com>