Add some nextcloud apps
Janek proposed to add some nextcloud apps, see !1208 (closed) . We have been conservative about that in the past, as we wouldn't like to enable a lot of software that we don't use ourselves, because we wouldn't even notice if things degrade or break. I'd like to discuss what our policy is exactly, and maybe together go through the list of proposed additions to see if there's anything we want to add now.