Move DarkConsole to an application

Summary: Ref T5702. Primarily, this gets the custom DarkConsole URI routes out of the Aphront core and into an Application, like almost all other routes.

Test Plan: Used DarkConsole.

Reviewers: btrahan

Reviewed By: btrahan

Subscribers: epriestley

Maniphest Tasks: T5702

Differential Revision: https://secure.phabricator.com/D10695