Extract User.ensureUserByUsername(...) from related_users resource

Also clean up related_users resource code
Fix hogwarts.opinsys.net rest-api for dev env
Move UpdateMixin to SelectUsers

for some reason it does not work from the Lightbox component. Must
investigate later...
Fix url building for utils.Puavo
Enable process wide Bluebird debug

for non-production environments. In other words we get better and longer
stack traces.
Save handlers to db