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.
Sorry, just spotted this. #76-#83 seems like a big chunk of code to have a post-conditional. I'd find it clearer to be a normal if-statement around the each block.