Mark All messages of a discussion as read to reduce data consumption

Requires a Modle 3.2 sites for testing Double check that the Message output "Web" is enabled in /admin/message.php Create 2 users (senders) and one more (receiver). Using the senders, send messages to the receiver (you can use website or app). Go to messages and enter a discussion. Check you can see where the unread messages starts. (New message text will be shown on top of the unread messages). Go back and enter again and check all messages are now read. (no blue text shown).