Re-arrange index to include more general info toward the top.
Re-order release note links in the index to be consistent, with
the latest at the top.
Add a summary description of each of the deploy references.
Fix broken link from find-us.html to Online Meetings.
Fix broken 'reviews' reference from how-to-contribute.html.
Change-Id: Id44d609d4e083b68c9a35db6798f59195a986906
Ryan Beisner