[Sprint/PinkPanther](feat): Put unread conversations to top of conversation list

Closes #819 (closed)

Summary

Unread messages were not appearing top of the messenger list which could lead to lost conversations.

Reproduce

1. Get 3 browsers open.
2. Log in to 3 seperate accounts.
3. All message your main user.
4. Load your conversation list on the main user, and click the top one.
5. Close the messenger popup and re-open it. - you should observe that the read user is below the unread.
6. Experiment, and make sure chronological order is respected, but unread conversations are top.