almost-CR version of Semantics

I fixed up a couple of things in Semantics (dates, pointer to test suite 
landing page).  I didn't change the status from ED to CR.

However, there are still outstanding unresolved comments, one of which will 
require a minor change to -Semantics even if the commenter is happy with the 
proposed resolution.

So the version at 
https://dvcs.w3.org/hg/rdf/raw-file/default/rdf-mt/index.html should be 
extremely close to a CR version.   Complain if something is wrong!

peter