Deploy to GAE: Shouldn't use (deprecated with GAE) JDO

[murraycu]

The "Deploy to GAE" page
http://www.gwtproject.org/doc/latest/tutorial/appengine.html#user
shows how to use JDO, but Google currently suggest not using JDO, and instead using Objectify:
https://cloud.google.com/appengine/docs/java/datastore/jdo/overview-dn2