Support for organisations/shared folders/shared ACLs/something similar

[csmith]

It'd be nice if there were a way to share a bunch of domains with a set of users, and have a single place to modify which users/access levels/etc. e.g. the domains that belong to a business can be shared with the relevant people but they'll all need to be updated together.

Could be done with full blown organisations (ala GitHub), or making it so you can share folders (#56), or some kind of separate ACL system.