Downloads Page

There are still a few things left from comments on #1 that need to be addressed. I'll probably add commits here...

I have deleted my fork, so all changes are now live at: http://musicbrainz.github.io/picard-website/
Now that we're duplicating content between pages (e.g. the header, footer), and since you mentioned that you'd be writing the download counter in flask, I was wondering what your plans are for moving this all to templates in general. (Having static pages while you're working out the design is okay, although it gets messy when I leave comments like "s/Docs/Documentation/" below because it means you now have to fix it in every page.)