Users manager basic

This adds a basic Users manager (a way to see users for admins, and for them to manage membership in the configured global teams), e.g.:

It's super basic, but it allows usage of global teams (teams that are not based around an object, such as a collection, instead the object of global teams is undefined).

Both TeamsManager and UsersManager have been debootstrapified, so they look even more basic. :)