improve smartness for Unity case layout

--when a vertical view is in busy state and is touching
also a horizontal view that is fully transparent in
SMART mode then the visual result is not that good.
In that case it is better to show the view background.
The horizontal view background in that case can provide
three different states:
a) if the panel style for popups is activated then the
horizontal view will follow the plasma original style
b) if NOT [a] and solid background for touching windows
is enabled then solid background will be offered
c) if NOT [a] and NOT [b] then the isBusy state
transparency will be offered