R1:45ff6077a7c7

Allow standard fields to have defaults

Summary: Final standard capability from Maniphest fields.

Test Plan: This isn't really reachable now since users always exist, but faked it and verified the field prefilled as expected.

Reviewers: btrahan

Reviewed By: btrahan

CC: aran

Differential Revision: https://secure.phabricator.com/D7033