Change usernames to sort64 to make them case-insensitive
Summary: Ref T1191. After adjustment, usernames currently end up case-sensitive, which means alincoln and Alincoln are different users. Make them case-sensitive so these names collie.
Test Plan: Ran bin/storage adjust.
Reviewed By: btrahan
Maniphest Tasks: T1191
Differential Revision: https://secure.phabricator.com/D10786