Migrate Project image to modular transactions

Summary: I'm not sure you can actually remove a project's image (maybe via the API?), but I kept the code for rendering the relevant title/feed anyway.

Test Plan: Unit tests + adding/changing project pictures.

Reviewers: #blessed_reviewers, epriestley

Reviewed By: #blessed_reviewers, epriestley

Subscribers: Korvin, epriestley

Differential Revision: https://secure.phabricator.com/D17954

src/applications/project/controller/PhabricatorProjectEditPictureController.php

@@ -78,7 +78,8 @@ final class PhabricatorProjectEditPictureController
 
         $xactions = array();
         $xactions[] = id(new PhabricatorProjectTransaction())
-          ->setTransactionType(PhabricatorProjectTransaction::TYPE_IMAGE)
+          ->setTransactionType(
+              PhabricatorProjectImageTransaction::TRANSACTIONTYPE)
           ->setNewValue($new_value);
 
         $editor = id(new PhabricatorProjectTransactionEditor())