Creates system accounts/groups; corresponds to the '-r' option for {user,group}add.
The option is only honored when users/groups are added, not when modified.
This relies on groupadd, groupmod, groupdel, and gpasswd utilities on
the system. You can optionally modify the gid for the group. You can
also add/remove a user to/from a group with the option member. Member
state is defined with the option memberstate.
