Updated Versioning finding

I've updated all 3 TAG versioning finding documents to reflect our May
f2f discussions, Noah, Stuart, Dan, and Rhys's email comments, and
various other things that have occurred to me.

The permanent URIs for this version are at 
http://www.w3.org/2001/tag/doc/versioning-20070704.html
http://www.w3.org/2001/tag/doc/versioning-strategies-20070704.html
http://www.w3.org/2001/tag/doc/versioning-xml-20070704.html

And the always latest version documents are at 
http://www.w3.org/2001/tag/doc/versioning
http://www.w3.org/2001/tag/doc/versioning-strategies
http://www.w3.org/2001/tag/doc/versioning-xml

Cheers,
Dave