Up to now the UI appearance on all platforms was aligned as much as
possible with stylesheets. Since the base widget styles still were
platform dependent defaults, there were many small differences in
details and controls. Some of them were even broken. Instead of
trying to tweak all platform specific styles, default to one on all
platforms. This guarantees that the UI is truly cross platform and
all styles and fixes cover all platforms at the same time.
For users who want to change the default style, they have now a gui
setting. But it is strongly recommended to stick with the default.
refs #683
