Rename PHIDType classes

Summary: Ref T5655. Rename `PhabricatorPHIDType` subclasses for clarity (see discussion in D9839). I'm not too keen on some of the resulting class names, so feel free to suggest alternatives.

Test Plan: Ran unit tests.

Reviewers: epriestley, #blessed_reviewers

Reviewed By: epriestley, #blessed_reviewers

Subscribers: epriestley, Korvin, hach-que

Maniphest Tasks: T5655

Differential Revision: https://secure.phabricator.com/D9986

src/applications/files/phid/PhabricatorFileFilePHIDType.php

@@ -1,6 +1,6 @@
 <?php
 
-final class PhabricatorFilePHIDTypeFile extends PhabricatorPHIDType {
+final class PhabricatorFileFilePHIDType extends PhabricatorPHIDType {
 
   const TYPECONST = 'FILE';