Markdown

@mmontone, @tplotnikov, @vdardel: this branch adds markdown processing but generates a horrible TOC (and doesn't recognize the "Awesome" image/link).

The "Awesome" image/link might be a further improvement, but if we can convince this branch to create an acceptable ToC, I'd think we're a long way towards migrating a few important pages to Markdown.

The pages which I'd like to be Markdown most of all are the news page (which it already is) and the "project-intro" page, simply because I have to rewrite it completely. Which also explains why I'd like to have the ToC (project-intro uses that) but not so much about the "Awesome" image/link (project-intro doesn't use it; neither does news).

Closes #9 (closed).