Pholio - allow Pholio Mocks to be attached to Maniphest Tasks (and vice versa)

Summary: Fixes T2654.

Test Plan: attached lots of mocks and tasks to one another from both maniphest and pholio. verified transactions rendered okay in both applications

Reviewers: epriestley

Reviewed By: epriestley

CC: aran, Korvin

Maniphest Tasks: T2654

Differential Revision: https://secure.phabricator.com/D6501