Created by: MartijnCuppens
Add all remaining utilities to the utility API. I needed to tweak the mixin a bit to make it work for the visibility mixins.
I've also dropped the :hover and :focus states of a.text-* color utilities and instead added new .link-* helper classes. This way there's a stricter distinction between helpers and utilities: helpers handle more than one property and utilities only take care of one single property without hover or focus states.