The user account management needs refactoring

Description / Overview

The current user model is partly broken. We need a general discussion about how to do authentication and how much effort should be spent on it. The current changes in the refactor branch are not satisfying (a lot of code that needs to be maintained for almost no additional use). Currently we use a combination of Option 2 and 3 of [1].

Simply using the abstract user might be the sanest approach.

Links / references

• [1] Possible optinons
• [2] Django docs

Feature checklist

• Adding information to a User is simple.
• Changing user information in the admin interface works as expected. See #40 (closed).
• The user object of HTTP requests in views can be easily distinguished. E.g. model contains info about group and associated pages.
• Django auth groups are not used.