Fix nightly docs link, update JDBC driver link

The nightly docs location seems to have moved, and
the CNAME/redirect that was working before is broken,
so fix it to point to the right link.

Furthermore point to the new JDBC driver release on
the site.

Change-Id:If17ec8dbd1de435c9a0c6e9f4d3b71c6ede2a5b1
Reviewed-on: https://asterix-gerrit.ics.uci.edu/c/incubator-asterixdb-site/+/20938
Reviewed-by: Ian Maxon <imaxon@apache.org>