new Primer

Hi all,

In the spirit of "sometimes you have to throw one away," I've rewritten 
the Primer from scratch. I've tried as best as I could to take into 
account your various comments, in particular finding examples that 
require less explanation of details such as xsd:date.

I've also made the language quite a bit simpler, and, most importantly, 
I've added a whole bunch of diagrams.

So... read this with an open (data) mind, and let me know what you 
think! Version not date frozen on purpose, I expect feedback :)

http://www.w3.org/2006/07/SWD/RDFa/primer/

-Ben