Add creator/admin permissions for groups, with optional independent section separation

closing as duplicate of Admin/mod roles, and prevent people from removing others from group - it does not matter, how old a feature proposal is, they’re still duplicates. note that there are more than 1000 feature proposals here, nearly one new per day. so, there is lots of triage, considerations not that easy to grep. everyone has its own priorities, and of course wants to get the handled as such. anyway, posting duplicates does not make things faster - it just keeps the team unnecessarily busy with moderation :slight_smile: