Add common styling for avatars.
Review Request #10445 — Created March 13, 2019 and submitted
We previously styled avatars differently in different parts of the UI.
Most places would style the avatars to be rounded, but some places would
not, and it entirely depended on where the avatar was.
This adds some common styling that gives avatars a rounded look by
default. Places that need to show a square view (such as the infobox)
can (and currently do) override the
border-radiusto remove the
Looked around the UI for all places where we use avatars, both in
Review Board and RBCommons, checking that they appeared as expected.