KControl cleanup

[Benoit Walter]

> I've wondered for a while why we have such old-looking "previews" in the
> Colors module and in the KWin Buttons module. The look of the preview
> hasn't changed since KDE1... I realize it's extremely unlikely that we'd be
> able to fix this before the 3.2 release, but I'd like to take a look at
> using realtime current-style and current-window-deco previews with the
> Colors module and the KWin Buttons module before KDE 3.3.

Those kcms are likely to be changed in 3.3 in favor of a single kcm (with a 
single preview).