R1:330b0a3d4b9c

Make projects policy-aware

Summary: We managed to move enough Owners stuff aside to make this reasonable; make projects implement the policy interface and projectquery use cursor-based paging.

Test Plan:
- Grepped for ProjectQuery callsites.
- Created an audit comment.
- Used `project.query` to query projects.
- Loaded homepage.
- Viewed Maniphest task list, grouped by project.
- Viewed project list.
- Created / edited project.
- Browsed Owners.

Reviewers: vrana, btrahan

Reviewed By…