Add NewUserHandler. Give existing handler functions better names.

Issue #DC-9 In Progress
Issue #DC-9 work 5m Add NewUserHandler stub function.
Add user type to package 'data'. Create user object on registration.

Issue #DC-9 work 1h Implement user create handler.
Issue #DC-10 In Progress
Issue #DC-10 work 1h Implement initial user data type.