Rename PhabricatorUIExample subclasses for consistency

Summary: Ref T5655. Basically, rename all PhabricatorUIExample subclasses to be either Phabricator*UIExample or PHUI*Example.

Test Plan: arc lint and arc unit.

Reviewers: epriestley, Blessed Reviewers

Reviewed By: epriestley, Blessed Reviewers

Subscribers: Korvin, epriestley

Maniphest Tasks: T5655

Differential Revision: https://secure.phabricator.com/D11177