Use a disk-based default avatar, not a database-based one

Summary:
This is mostly in an effort to simplify D2323. Currently, we load one image into the database by default. This is a weird special case that makes things more complicated than necessary.

Instead, use a disk-based default avatar.

Test Plan: Verified that a user without an image appears with the default avatar as a handle, in profile settings, and on their person page.

Reviewers: btrahan, vrana, edward, jungejason

Reviewed By: vrana

CC: aran

Maniphest Tasks: T345

Differential Revision: https://secure.phabricator.com/D2331

src/applications/project/controller/profile/PhabricatorProjectProfileController.php

@@ -49,7 +49,7 @@ final class PhabricatorProjectProfileController
     if ($file) {
       $picture = $file->getBestURI();
     } else {
-      $picture = null;
+      $picture = PhabricatorUser::getDefaultProfileImageURI();
     }
 
     $members = mpull($project->loadAffiliations(), null, 'getUserPHID');

src/applications/project/controller/profile/__init__.php

@@ -12,6 +12,7 @@ phutil_require_module('phabricator', 'applications/feed/query');
 phutil_require_module('phabricator', 'applications/files/storage/file');
 phutil_require_module('phabricator', 'applications/maniphest/query');
 phutil_require_module('phabricator', 'applications/maniphest/view/tasksummary');
+phutil_require_module('phabricator', 'applications/people/storage/user');
 phutil_require_module('phabricator', 'applications/phid/handle/data');
 phutil_require_module('phabricator', 'applications/project/controller/base');
 phutil_require_module('phabricator', 'applications/project/storage/profile');