R1:22ee37e8b528

Make the `PhabricatorApplication::getName()` method abstract

Summary: In D10027, the `getName()` method was added to `PhabricatorApplication` to //allow// applications to explicitly declare their names rather than relying on the name being inferred from the name of the `PhabricatorApplication` subclass. I feel that sufficient time has passed such that we can //require// applications to explicitly declare their names.

Test Plan: N/A

Reviewers: epriestley, #blessed_reviewers

Reviewed By: epriestley…