Improve default smart zoom

[soerendomroes]

Calculate opacity based on title color or overlay background. (potentially also take the scalingfactor into account as an approximation to get better results in most cases)

Regions shouldn't be omitted in superstates as that is semantically strange. In this case the synthesis should set a property that tells the client to not apply smart zoom to the superstates.

Placeholder symbol for hidden contents is now turned off by default, the rendering should be given by synthesis.

[soerendomroes]

Maybe rounded rect instead of rect for title backgrounds?

[NiklasRentzCAU]

Not complete yet, revoke autoclose by commit message