Use application PHIDs in countdown

Summary: Ref T2715. Swap countdown to application PHIDs.

Test Plan: Used `phid.lookup`; `phid.query`.

Reviewers: btrahan

Reviewed By: btrahan

CC: aran

Maniphest Tasks: T2715

Differential Revision: https://secure.phabricator.com/D6532
Fix "setName()" on Differental revision handles

Summary: I copied this over wrong. Ref T2715

Test Plan: Looked at Maniphest with linked commits/revisions, e.g.

Reviewers: btrahan

Reviewed By: btrahan

CC: aran

Maniphest Tasks: T2715

Differential Revision: https://secure.phabricator.com/D6531