* Refactor: re-arrange test application
This was triggered by the need to run "python manage.py", which is impossible when serving the whole project in the same directory as is configured in INSTALLED_APPS ("auditlog_tests"). This setup is heavily inspired by other jazzband projects.
* Add check for missing migrations
* run postgres query for rows that changes is null for them and there is value for changes_text
* add a test case to make when changes has value it wont be overwritten by changes_text
