Use Header palette if exists
Essentially the same as !5 though a bit more smart, it checks for Header color support and fallbacks to classic WM colors if there's none. Also adds a new palette called "header" for GTK coloring support which will be used in Breeze-GTK for a menubar (and maybe toolbar) coloring. ![изображение](/uploads/3f292a28a7824d67709c547860df5a72/изображение.png)