Implement Project Interface in PhabricatorRepository

Summary: T2628, PhabricatoryRepository.php now implements PhabricatorProjectInterface

Test Plan: Verify project tags still work in phabricator repositories

Reviewers: epriestley, #blessed_reviewers

Reviewed By: epriestley, #blessed_reviewers

Subscribers: epriestley, Korvin

Differential Revision: https://secure.phabricator.com/D9683