Use "Diff <id>" instead of "D<id>" in changeset view

Summary: We use "D<id>" for revisions.

Test Plan: Looked at revision.

Reviewers: btrahan, epriestley

Reviewed By: epriestley

CC: aran, Korvin

Differential Revision: https://secure.phabricator.com/D4258

src/applications/differential/controller/DifferentialDiffViewController.php

@@ -133,7 +133,7 @@ final class DifferentialDiffViewController extends DifferentialController {
       ->setRenderingReferences($refs)
       ->setStandaloneURI('/differential/changeset/')
       ->setDiff($diff)
-      ->setTitle('D'.$diff->getID())
+      ->setTitle('Diff '.$diff->getID())
       ->setUser($request->getUser());
 
     return $this->buildStandardPageResponse(