Add indicator to chat list view about expired messages

[HenrikJannsen]

The notifications might signal there are more unseen messages as there are in reality due to expired messages. Also it gives a wrong impression to see channels without any messages without the info that past messages have been removed due expiration date. We could add a special list entry as first in the list in case there have been messages in the past (or add it by default to all as over time all channels will have had expired messages). This entry could give a basic info that messages have a time to life and gets removed from the network after that time. This would be useful info to users as most will not be aware of that.