Implement bin/remove, for structured destruction of objects

Summary:
Ref T4749. Ref T3265. Ref T4909. Several goals here:

  - Move user destruction to the CLI to limit the power of rogue admins.
  - Start consolidating all "destroy named object" scripts into a single UI, to make it easier to know how to destroy things.
  - Structure object destruction so we can do a better and more automatic job of cleaning up transactions, edges, search indexes, etc.
  - Log when we destroy objects so there's a record if data goes missing.

Test Plan: Used `bin/remove destroy` to destroy several users.

Reviewers: btrahan

Reviewed By: btrahan

Subscribers: epriestley

Maniphest Tasks: T3265, T4749, T4909

Differential Revision: https://secure.phabricator.com/D8940