Consolidate Macro loading

Summary:
Fixes T2820

Grepped for `PhabricatorFileImageMacro`, a common approach to load image macros from storage. Cleaned up file loading too (in most cases where I could be sure that I won't break anything).

Did not touch the `add_macro.php` util script, since many users will assume the user `ubuntu` or `ec2-user` to run the script. Add no sessions and no CSRF protection measures...

Test Plan:
Browsed around all kinds of places. Created and looked at memes, created and edited macros. Used them in Remarkup (with flushed cache). Used `macro.query`, verified it did not crash (that's always a good sign).

Could not verify object handles, since I have no idea where they appear right now.

Reviewers: epriestley

Reviewed By: epriestley

CC: aran, Korvin

Maniphest Tasks: T2820

Differential Revision: https://secure.phabricator.com/D5418

src/applications/macro/controller/PhabricatorMacroMemeController.php

@@ -9,14 +9,14 @@ final class PhabricatorMacroMemeController
     $upper_text = $request->getStr('uppertext');
     $lower_text = $request->getStr('lowertext');
     $user = $request->getUser();
-    $macro = id(new PhabricatorFileImageMacro())
-      ->loadOneWhere('name=%s', $macro_name);
+    $macro = id(new PhabricatorMacroQuery())
+      ->setViewer($user)
+      ->withNames(array($macro_name))
+      ->executeOne();
     if (!$macro) {
       return new Aphront404Response();
     }
-    $file = id(new PhabricatorFile())->loadOneWhere(
-      'phid = %s',
-      $macro->getFilePHID());
+    $file = $macro->getFile();
 
     $upper_text = strtoupper($upper_text);
     $lower_text = strtoupper($lower_text);