Make projects appear in all mailable tokenizers

Summary: Ref T4361. Projects are mailable now, so let them show up in mail contexts.

Test Plan: Added a project as a CC to a task, filtered by project CCs, etc.

Reviewers: btrahan, zeeg, dctrwatson

Reviewed By: btrahan

CC: aran

Maniphest Tasks: T4361

Differential Revision: https://secure.phabricator.com/D8274