Move Releeph branch controllers toward a modern/stable state

Summary:
Ref T3644. Ref T3657. Ref T3549. Basically:

  - Move these controllers to modern query/policy infrastructure.
  - Move them to consistent, ID-based URIs.
  - Rename "Project" to "Product"; "Pick Request" to "Pull Request".
  - Clean up a few UI things here and there.

Test Plan:
  - Created and edited branches.
  - Opened and closed branches.
  - Viewed branch history.
  - Searched within a branch.
  - Browsed to branches from products.

Reviewers: chad, btrahan

Reviewed By: btrahan

Subscribers: epriestley

Maniphest Tasks: T3644, T3549, T3657

Differential Revision: https://secure.phabricator.com/D8646