Add "final" to all Phabricator "Controller" classes

Summary:
These are all unambiguously unextensible. Issues I hit:

  - Maniphest Change/Diff controllers, just consolidated them.
  - Some search controllers incorrectly extend from "Search" but should extend from "SearchBase". This has no runtime effects.
  - D1836 introduced a closure, which we don't handle correctly (somewhat on purpose; we target PHP 5.2). See T962.

Test Plan: Ran "testEverythingImplemented" unit test to identify classes extending from `final` classes. Resolved issues.

Reviewers: btrahan

Reviewed By: btrahan

CC: aran, epriestley

Maniphest Tasks: T795

Differential Revision: https://secure.phabricator.com/D1843

src/applications/diffusion/controller/home/DiffusionHomeController.php

@@ -1,7 +1,7 @@
 <?php
 
 /*
- * Copyright 2011 Facebook, Inc.
+ * Copyright 2012 Facebook, Inc.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -16,7 +16,7 @@
  * limitations under the License.
  */
 
-class DiffusionHomeController extends DiffusionController {
+final class DiffusionHomeController extends DiffusionController {
 
   public function processRequest() {
     $request = $this->getRequest();