Django-4.2 support

• Support for Django-4.2
• Follow model relations across apps
  (This once was the default but changed unintendend with 4.1 by using the modeltree lib.)

2.1

• fixed a permission issue: #10
• use django-modeltree library

Support django-4.0 and 4.1

• Added support for django 4.0 and 4.1
• Skipped support for django 1.11, 2.0 and 2.1