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