Publish additional context to the Aphlict server.

Summary:
Ref T4324. As well as sending the key for the notification, also publish the notification type and a list of subscribers to the Aphlict server.

The idea here is that the Aphlict server passes anything within the `data` key to the clients, whereas other keys (such as `subscribers`) will be used by the server to determine where the notifications should be routed.

Note that these changes don't do anything useful, but are a prerequisite for further work on T4324.

Test Plan:
Sent myself test notifications at `/notification/status/`. Also inspected the Aphlict server debug output:

```
> sudo ./bin/aphlict --foreground
Starting server in foreground, ignoring pidfile...
Launching server:

    $ node '/usr/src/phabricator/support/aphlict/server/aphlict_server.js' --port='22280' --admin='22281' --host='localhost' --user='aphlict' --log='/var/log/aphlict.log'

[Thu Jun 05 2014 18:38:14 GMT+0000 (UTC)] Started Server (PID 15437)
[Thu Jun 05 2014 18:38:16 GMT+0000 (UTC)] <FlashPolicy> Policy Request From ::ffff:10.0.0.1
[Thu Jun 05 2014 18:38:16 GMT+0000 (UTC)] <Listener/1> Connected from ::ffff:10.0.0.1
[Thu Jun 05 2014 18:38:19 GMT+0000 (UTC)] notification: {"data":{"key":"6021516228036848559","type":"notification"},"subscribers":["PHID-USER-cb5af6p4oepy5tlgqypi"]}
[Thu Jun 05 2014 18:38:19 GMT+0000 (UTC)] <Listener/1> Wrote Message
```

Reviewers: epriestley, #blessed_reviewers

Reviewed By: epriestley, #blessed_reviewers

Subscribers: epriestley, Korvin

Maniphest Tasks: T4324

Differential Revision: https://secure.phabricator.com/D9396

Author: joshuaspence

src/applications/feed/PhabricatorFeedStoryPublisher.php

@@ -175,9 +175,12 @@ private function insertNotifications($chrono_key) {
   }
 
   private function sendNotification($chrono_key) {
-
     $data = array(
-      'key' => (string)$chrono_key,
+      'data' => array(
+        'key'  => (string)$chrono_key,
+        'type' => 'notification',
+      ),
+      'subscribers' => $this->subscribedPHIDs,
     );
 
     try {

src/applications/notification/client/PhabricatorNotificationClient.php

@@ -2,7 +2,7 @@
 
 final class PhabricatorNotificationClient {
 
-  const EXPECT_VERSION = 4;
+  const EXPECT_VERSION = 5;
 
   public static function getServerStatus() {
     $uri = PhabricatorEnv::getEnvConfig('notification.server-uri');

support/aphlict/server/aphlict_server.js

@@ -120,9 +120,9 @@ var receive_server = http.createServer(function(request, response) {
     request.on('end', function () {
       ++messages_in;
 
-      var data = JSON.parse(body);
-      debug.log('notification: ' + JSON.stringify(data));
-      broadcast(data);
+      var msg = JSON.parse(body);
+      debug.log('notification: ' + JSON.stringify(msg));
+      broadcast(msg.data);
       response.end();
     });
   } else if (request.url == '/status/') {
@@ -139,7 +139,7 @@ var receive_server = http.createServer(function(request, response) {
         'messages.in': messages_in,
         'messages.out': messages_out,
         'log': config.log,
-        'version': 4
+        'version': 5
       };
 
       response.write(JSON.stringify(status));