Require User.fullname to be populated

[mikerkelly]

User.fullname is a TextField that defaults to an empty string. There are 27 User on the live server with fullname == ''. If we can manually fill in that field for each that would allow us to enforce fullname being populated in both the model and views/forms (non-null and non-empty?). That could allow us to be rid of the User.name property which uses fullname but falls back to username if fullname is empty. This would simplify the User model and populated the DB with better data for managing or viewing User instances.