#268 Allow Admin to list/change subscriptions on other lists

[NancyS]

While I understand some of the reasons why allowing an admin to list/change subscriptions on other lists may not be appropriate for all installations, I'd like to see this pre-2.1.9 functionality return to Mailman.

Perhaps it could be implemented as an option on a per-virtual-domain basis. For virtual domains where all the lists support one community and are administered by the same people, allowing an administrator to, say, change a subscriber's address on all the lists at one time is invaluable.