Split off from  bug 859427 .

Background: For "not useful" reports, we may want to record the user ID of the person who clicks "not useful", in case there are many reports from one person, this should be treated differently than reports from different people.

It appears that reporting not useful in gerrit-review worked for ekempin@google.com but not david.pursehouse@gmail.com. I think ideally anybody logged into Gerrit should be able to report comments as not useful on that Gerrit instance.