Migrate Project edges to subclass PhabricatorEdgeType
Summary: Modernize Project edges to subclass PhabricatorEdgeType. Largely based on D11045.
Test Plan: Add a member to a project, saw new rows in the phabricator_project.edge and phabricator_user.edge tables.
Reviewers: epriestley, #blessed_reviewers
Reviewed By: epriestley, #blessed_reviewers
Subscribers: Korvin, epriestley
Differential Revision: https://secure.phabricator.com/D11111