UI to manage API users

www.agileplannerapp.com/boards/173808/cards/4993

introducing a UI to:
1. list, create, edit, suspend API users
2. create, revoke and regenerate tokens for API users

see commit messages for additional information.
Chosen modules are started using data attributes now: see https://github.com/alphagov/signonotron2/commit/4d21227555015453d09b8908d1944e6ec2380c15