R1:fe9ba6bc67dd

Improve DifferentialRevisionQuery and add the ability to query by arcanist project

Summary:
- We currently post-filter by branches, but should do this in SQL. See T799.
- We currently identify branch-name-matches as being in the working copy even if they belong to a different project (e.g., two different projects with commits on the branch "master"). See T1100.
- Denormalize branch and project information into DifferentialRevision.
- Expose project information in the API.

Test Plan: Ran conduit…