Add or complete docstrings
Remove code smells
Disable irrelevant warnings
Update translations to changed line numbers and line breaks
Move duplicated code for event field pre-population and event timezone adaption to mixins

This is the base for custom admin views (with admin design and permission checking)
Replace default admin site with custom admin site in AKModel
Use custom admin index template & apply first basic change
Introduce custom admin base template (including bootstrap loading)
Introduce Mixin for AdminViews