Rework of wiki main page

I've done a quick revamp of the main wiki page, based on some of the tables
we added to the FOAF wiki.

Not much has really changed, but hopefully slightly better styles and
organization.

http://www.w3.org/community/rww/wiki/Main_Page

Let me know if there's anything you'd like to see added moved etc.  Then
again, it's a wiki, so feel free to dive in! :)