i.e. trasform XYZ bytes to something readable

Allow `colorN' and `colourN' (where 0 <= N < 256) as color specifier.

`attr' now follows the same rule as `fg' and `bg', with the three airity variant. Attributes by themselves are a comma-separated list of keywords, each one representing a ncurses attribute.

now, instead of prefix and line style, I'm adding the trailing style too. This changed the configuration syntax too.