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