Ability to rename an organization (team site)

[fflorent]

After #903 has been implemented, a user has reported that he could not find how to rename the team site he created.

There is already a API endpoint that can be called, but that is a bit technical for users. Unless I am wrong, I think there is currently no other way.

That should be easy to be implemented regarding the development itself, still it would need some design work beforehand.

cc @lusebille

[paulfitz]

Thanks @fflorent. It is is at all helpful as a design reference, our SaaS billing system has this functionality (you can see it on free team sites). It might be as easy to start fresh though, since our design isn't particularly pretty.