Removed Inbox from core (unused since 4b2a66ed29)

Added the following FIXME:
How should a Twitter user get their Inbox filled with foreign tweets?

Every imported Twitter user has a profile in the Profile table, so we
could setup a Subscription entry for each of those, meaning they get
collected in the InboxNoticeStream... But this would mean a lot of
unnecessary entries and listings that generally just point to the
locked down Twitter service.

Let's figure out a good relation so we can connect any profile to any
imported foreign notice, so it shows up in the "all" feed.

classes/User.php

@@ -325,20 +325,6 @@ class User extends Managed_DataObject
                 return false;
             }
 
-            // Everyone gets an inbox
-
-            $inbox = new Inbox();
-
-            $inbox->user_id = $user->id;
-            $inbox->notice_ids = '';
-
-            $result = $inbox->insert();
-
-            if (!$result) {
-                common_log_db_error($inbox, 'INSERT', __FILE__);
-                return false;
-            }
-
             // Everyone is subscribed to themself
 
             $subscription = new Subscription();