Always display Branch in revision

Summary:
I, as an author, sometimes forget branch associated with a revision.
Plus setting differential.show-host-field makes a false sense of security
that branch will stay hidden so that I can name it
finally_solve_this_crap_which_makes_no_sense. But it is published in
Accepted and Request Changes e-mails anyway.

Test Plan: Display revision with disabled differential.show-host-field.

Reviewers: epriestley

Reviewed By: epriestley

CC: aran, epriestley

Differential Revision: https://secure.phabricator.com/D1602