Users can create groups

[mreider]

This is a backend story only for now.

• Groups have names. "My chess club."
• Groups have descriptions "a place where people talk about chess"
• Groups have images (like users)
• Groups can be public or private
• Groups have only one admin (the creator)
• Members can leave a group at any time.
• Members of groups can see a list of other members, just like when you look at a friend's list of friends.
• They can also make friend requests from these pages.
• When someone joins a group, they become friends with the admin (if they aren't already).
• A group post will be saved on the message hub where the group admin belongs. This means people can join groups as a way to join koto, instead of having to find a friend who might have a message hub.
• Group posts and messages have the same functionality in terms of likes, comments, links, markdown, etc.
• Admins can choose friends to put in groups without their permission.
• Not all message hubs support public groups. When a user creates a message hub, they can choose to support groups or not.
• For public groups - users must request to join the group with an optional message
• Member requests for public groups are received by the group admin just like friend requests
• Group admins can approve or deny membership. If they deny membership, the user does not become friends.
• Group admins can remove users. This does not effect their friendship.