integrated Manu's edits into the Primer

Hi all,

I've integrated as much of Manu's edits into the Primer as possible. A
few comments:

- I used the new example idea of a BBQ... the changes were fairly
contained, so I went for it.

- I simplified as much as I could, but I didn't integrate every
suggested change, mostly because I think some of the suggested changes
might have oversimplified the description a bit too much... but that was
only 10% of the suggestions.

- I'm still working on the missing sections, more on this tomorrow...

When I'm done tomorrow, I'll freeze the version with a timestamped URL.
Right now, edits are still at:

http://www.w3.org/2006/07/SWD/RDFa/primer/
$Id: Overview.xml,v 1.22 2007/09/10 03:49:21 adida Exp $

-Ben