We now only render a user's full name only if they have a public

profile. In other cases, we fall back to the username when appropriate

or render an empty string (such as in the full name column).
We now also provide the {% user_profile_display_name %} template tag,

which will render a user's full name is visible to the current user, or

their username if not. This should be used in place of the

user_displayname filter.
This change also addresses a regression introduced by Djblets in 

https://reviews.reviewboard.org/r/9955/ where the avatar template

changed, causing test failures in Review Board. We now specify our own

avatar template (that uses our new template tag) and the unit tests have

been corrected

Ran unit tests.