Trivial review replies can be published, that is, published without

sending an e-mail notification.
This patch also fixes up some of the semantics in the review request

publishing. The not-trivial id has been changed to a send-email

class as it makes a bit more semantic sense.
NB: This is heavily based on Jessica Qian's work in

https://reviews.reviewboard.org/r/7125/

Ran unit tests. Ran JS tests.
Tested both review reply and review request publishing with and without

the "Send E-Mail" box checked. It works as expected.
Tested that the "Send E-Mail" checkboxes do not appear when e-mails are

disabled for the server.