Modernize Releeph "Product Activate" controller

Summary:
Ref T3549. A few things here:

• Releeph has an object called a "Project". We'd like to call this a "Product" instead. See T3549. Rename easy instances that don't break URIs.
• Releeph has a "ProjectController" which tries to be smart about loading objects. However, it's big and messy and doesn't have the finesse to do policies or needX(...) correctly. It also generates URIs which collide with one another. Introduce "ProductController" to start to move away from it.
• Some small modernizations to this controller to take advantage of newer infrastructure (like easier dialog rendering).

Test Plan: Deactivated and reactivated products.

Reviewers: btrahan

Reviewed By: btrahan

Subscribers: epriestley

Maniphest Tasks: T3549

Differential Revision: https://secure.phabricator.com/D8632