Monospaced alternate layout

This is a simple change that adds an alternate stylesheet (see http://www.w3.org/Style/Examples/007/alternatives.en.html)

There is need for a way to use a monospace characters for code, ascii-art and other stuff that requires monospaced fonts.

Most browsers will remember the last stylesheet used for the website, so this makes the change quite trivial, no javascript code modified.

It's also possible to add more alternate stylesheets in a similar way, pretty seamlessly.
The alternate layout makes use of "@import" to reuse the style from litewriter.css so that it's easy to mantain.