Sylvain thanks for the new documentation

[Sean Schofield <se...@gmail.com>]

I noticed Sylvain added some stuff to the website explaining the
extensions filter.  Good idea!  Lets try and update the site with new
documentation every few days.  Don't be afraid of the Forrest!  Its
not that bad!

This is another reason to automate the Forrest build.  Matthias is
gone and we have lots of improvements to the site sitting around for
days now.  When he gets back I will work with him to automate it.

sean