Modularize file transforms and provide a "transforms" UI

Summary:
Ref T7707. Available transforms are currently relatively hard-coded and don't really have any support UI.

Modularize them so we can build some support UI.

This doesn't actually //use// any of the new stuff yet: I want to make a clean cutover once I fix the aspect ratio stuff so I can pick up a cachekey/URI change as a side effect.

Test Plan: {F400524}

Reviewers: btrahan

Reviewed By: btrahan

Subscribers: chad, epriestley

Maniphest Tasks: T7707

Differential Revision: https://secure.phabricator.com/D12808

src/applications/files/controller/PhabricatorFileInfoController.php

@@ -170,6 +170,12 @@ final class PhabricatorFileInfoController extends PhabricatorFileController {
         ->setWorkflow(true)
         ->setDisabled(!$can_edit));
 
+    $view->addAction(
+      id(new PhabricatorActionView())
+        ->setName(pht('View Transforms'))
+        ->setIcon('fa-crop')
+        ->setHref($this->getApplicationURI("/transforms/{$id}/")));
+
     return $view;
   }
 
@@ -267,7 +273,6 @@ final class PhabricatorFileInfoController extends PhabricatorFileController {
         $user->renderHandleList($phids));
     }
 
-
     if ($file->isViewableImage()) {
       $image = phutil_tag(
         'img',