Move no owners exception logic to conversion method
Move owner lookup logic from get_owners to conversion method
Raise more generic exception types at conversion failure
Don't handle unknown location for future aktiviteter
Import relevant exceptions
Delete the original aktivitet-object on date conversion failure
Add ImportFailure model
Rename exception
Delete existing conversion failure objects
Rename ImportFailure -> ConversionFailure
Add cabin-relation field on conversion failures
Save conversion failure when occurring
Add initial failed_imports view
Remove unused row wrapper
Remove unnecessary 12-column row
Add link to failed imports from index page
List out failed imports
Add human-readable failure reasons
Add failed_imports javascript
Add clarifying help-text for failure reason