We now have two basic methods for CoreSelection
* when selecting a stripable, use ::select_stripable_and_maybe_group() with
appropriate arguments to cover the group selection aspects.
* when selecting an automation control that is part of a stripable, call
::select_stripable_with_control()
The old, more simply named methods (set/add/toggle etc.) have all been
made private, and their internal implementations changed somewhat.
This commit includes changes to control surfaces that use CoreSelection directly.
b21dd1212e