If there is a display name, it will be used in all views (task lists, task details, comments). Made a view for task lists, because it was cleaner and because they're all more or less the same anyway.
Added a "display name" field, which can be NULL. The field can be set from the user creation form, and is displayed in the list.
Added an user list page and a form to create new users. All users can create other users.
