edits to CG report

Prompted by comments from Jon and Connie today, I made several edits and 
we started a github issue <https://github.com/w3c/credweb/issues/3>
about one topic where it's unclear what to do.  So, as promised, I added 
a changelog at the end 
<https://credweb.org/report/snapshot.html#h.x3gfy680s059>.

Reminder: please review the doc and vote on releasing for public review, 
at your earliest convenience. If we have consensus a week from today, 
and no non-trivial changes for a couple days, we'll go forward with 
draft publication.

https://www.w3.org/2002/09/wbs/103073/report/

Thanks!

     -- Sandro