Profile Pictures can only be edited for System Agents

Summary:
I feel pretty disturbed by having the thought of admins,
super-beings among all users, being able to edit my profile picture. So I took away
that capability of theirs.

Test Plan: Tried to edit a sys agent's profile pic, and somebody else's.

Reviewers: epriestley, chad, btrahan, Afaque_Hussain

Reviewed By: epriestley

CC: aran, Korvin

Differential Revision: https://secure.phabricator.com/D5358

src/applications/people/controller/PhabricatorPeopleEditController.php

@@ -54,7 +54,9 @@ final class PhabricatorPeopleEditController
       pht('View Profile'), '/p/'.$user->getUsername().'/');
     $nav->addLabel(pht('Special'));
     $nav->addFilter('rename', pht('Change Username'));
+    if ($user->getIsSystemAgent()) {
       $nav->addFilter('picture', pht('Set Account Picture'));
+    }
     $nav->addFilter('delete', pht('Delete User'));
 
     if (!$user->getID()) {