BIC: Rework the api and appearance of the new HolidyRegionSelector widget.

After using the widget in the Plasma calendar I decided the api and layout
wasn't as usable as I wanted, and probably wouldn't scale well with planned
changes in 4.7. This change basically changes the gui from having two tick
boxes to displaying either a single tick box or a combo box with multiple
options. The api no longer refers to Primary or Secondary Selections but
instead uses flags with more meaningful names which should scale better when
holiday types and observance types are introduced and better separate the gui
implememtation from the api.