Store the "current" application in the controller

Summary:
When we match an application route, select it as the current application and store it on the controller.

Move routes for the major applications into their PhabricatorApplication classes so this works properly.

Test Plan: Added a var_dump() and made sure we picked the right app for all these applications.

Reviewers: vrana, btrahan

Reviewed By: vrana

CC: aran

Maniphest Tasks: T1569

Differential Revision: https://secure.phabricator.com/D3144