Turn view mode buttons into a combobox

Combobox is visually less noisy than three buttons, and also easier to grasp what it does, since it shows text by default. User can also use scrollwheel to toggle between views.

However this will need change to kselectaction.cpp in kwidgetsaddons to expose the comboBox->setFrame(); option. With the combobox frame this looks quite bad.

Alternatively we somehow modify it from here, but I think exposing it as a thing in kselectaction would make it easier.

Requires frameworks/kwidgetsaddons!289 (closed)

See also #68

Before	After	Without KWidgetsAddons Patch