Implement the `getName` method in `PhabricatorApplication` subclasses

Summary: Provide an implementation for the `getName` method rather than automagically determining the application name.

Test Plan: Saw reasonable application names in the launcher.

Reviewers: #blessed_reviewers, epriestley

Reviewed By: #blessed_reviewers, epriestley

Subscribers: epriestley, Korvin

Differential Revision: https://secure.phabricator.com/D10027