Summary: This makes all favicons a background circle w/color and white gear, to be less confusing to an actual gear icon.
Test Plan:
review many different versions in sandbox.
{F1811707,size=full}
Reviewers: epriestley, avivey
Reviewed By: avivey
Subscribers: Korvin
Differential Revision: https://secure.phabricator.com/D16539
