add page to allow admin to edit user details

[davewhiteland]

NB note although current logged-in user can't edit their own info, they can change their own password, which is OK

Admins can currently suspent a user, but they can't reset the password without going via db.

(This would also help slightly with set-up, since changing the admin user details is mandatory (there's a nag on the home screen until it's done) but currently requires it to be changed in the db directly)

[davewhiteland]

see also #3 which is presumably the best way to implement this!