forwardport 764429:
Revert the moving of the action to the DolphinView instance, this doesn't work with splitted views.
(Each view would need its own action collection, but then DolphinView would have to become
a KXMLGUIClient, and the GUI would flicker when switching views).
Instead, use the same solution as the other shared actions: static method in DolphinView (for now),
slot in the mainwindow (and for the more complex actions than this one, shared code in DolphinView)