Add bin/auth refresh for debugging OAuth token refresh issues
Summary: Ref T2852. Provide a script for inspecting/debugging OAuth token refresh.
Test Plan: Ran bin/auth refresh with various arguments, saw token refreshes.
Reviewers: btrahan
Reviewed By: btrahan
CC: aran
Maniphest Tasks: T2852
Differential Revision: https://secure.phabricator.com/D6276