Add a way to read "change volume" action's values from globals/formula

When you change volume with touch in KGWT, it would be nice to read values such as "Audio" or "Mode" from formula and/or globals, just like e.g. it's possible for "Open URL". Why? Simply to be able to create single consistently styled Komponent for e.g. 3 different (alarm, ringtone, media) volume types, currently it's impossible and you have to use copy & paste of grouped elements.

Globals/formulas need to be more consistent in general - some fields support both, some only formulas, some none.