Use google auto to save the day

Thanks to @eamonnmcmanus and @cgruber AutoValue (and also AutoService) are here to save us from writing tons of toStringHelpers, and from thrashing on guava versions of that. You'll notice that after using auto-value, these types are far easier to read. Whooot!

For tracking, this applies to our goal to reduce work in maintaining api model classes https://issues.apache.org/jira/browse/JCLOUDS-750