R1:5eb922fdb4ff

T870 - add a refresh button for sync'd OAuth accounts

Summary: nice title!

Test Plan: refreshed my profile pic against my OAuth Phabricator instance.

Reviewers: epriestley

Reviewed By: epriestley

CC: aran, epriestley

Maniphest Tasks: T870

Differential Revision: https://secure.phabricator.com/D1980