Show avatars in notifications and activity (like in server)

[tobiasKaminsky]

• Android @tobiasKaminsky
• Desktop @camilasan
• iOS @marinofaggiana
• Server @nextcloud/server-triage

Show avatars both in notification list and (if possible in push notifications)

[nickvergessen]

PS: only do this if it is in the rich subject.

Do not confuse this with the other story that is discussed in nextcloud/notifications#183
If that is done, it should be done in one step everywhere and you will be pinged again.