R1:94752278f4cd

Add a generic PHID-based object redirection controller

Summary:
Ref T13151. See PHI647. This allows us to link to any object by PHID, without disclosing information in the monogram (like `#fire-steve`).

This capability is relevant when building "secure mail", to provide a link to the object regardless of whether the monogram discloses information or not.

Test Plan: Visited `/object/D123/` (redirect), `/object/xyz/` (404), `/object/PHID-DREV-.../` (redirect).

Reviewers: amckinley

Reviewed By: amckinley…