Compile wall-post comment notifications

Instead of getting one notification, each time there is a new comment on our wall post, it would be neat to have them all in just one notification for more tidy notifications. The same way it works for topic notifications.

Thus, notifications could be worded as such:

Melcha Chen, Justin Finch-Fletchley and 3 others commented on your wall post.

To see who the other 3 people are, we can always just click on the notificarion and read these comments. 🙂