NanoUI fixes

- Fixes #6013
- Reverts temporary fix that removed the problem formatting (#6343)
- Renames red and yellow button classes to be more self explanatory
It actually has almost a kind of query-like syntax where you can select elements for which the formatting is applied.

I'm not much of an expert on CSS but I have to use it every now and then. [This reference](http://www.w3schools.com/cssref/css_selectors.asp) might be handy.