Display links to editor in Differential and Diffusion

Summary:
It is possible to open a file in editor by registering a custom URI scheme
(pseudo-protocol). Some editors register it by default.
Having links to open the file in external editor is productivity booster
although it is a little bit harder to set up.
There are several other tools using file_link_format configuration directive
(XDebug, Symfony) to bind to this protocol.
I've added the example with editor: protocol which can be used as a proxy to
actual editor (used by Nette Framework:
http://wiki.nette.org/en/howto-editor-link).

Test Plan:
Configure Editor Link in User Preferences.
Register URI scheme in OS.
Open a file in Diffusion. Click on the Edit button.
Open a revision in Differential. Click on the Edit button.

Reviewers: epriestley

Reviewed By: epriestley

CC: aran, epriestley

Differential Revision: https://secure.phabricator.com/D1422

src/applications/diffusion/controller/change/DiffusionChangeController.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.
@@ -44,6 +44,7 @@ class DiffusionChangeController extends DiffusionController {
       '/diffusion/'.$drequest->getRepository()->getCallsign().'/diff/');
     $changeset_view->setWhitespace(
       DifferentialChangesetParser::WHITESPACE_SHOW_ALL);
+    $changeset_view->setUser($this->getRequest()->getUser());
 
     $content[] = $this->buildCrumbs(
       array(