Package alterator-users: Information

- backend: Add group 'users' to default groups list.
- backend: Use installer default groups with libnss-role.
- backend: Add support for default-groups.d in the installer.

- Add display of groups to which the user belongs
- Add the ability to assign system roles to a user
- Default group is users when libnss-role is enabled.
  When creating a user, if libnss is enabled, the user is assigned a default
  group users.

- don't mess up multiseat autologin