Add is_imported model method
Add 'imported' label to imported aktiviteter
Disable save button for imported aktiviteter
Prevent saving imported aktiviteter server-side
Add button to trigger manual import
Let convert() raise ConversionImpossible; callers must handle
Handle ConversionImpossible on manual import trigger
Don't use alert wrapper for import info
Completely hide submit buttons for imported aktiviteter
Merge branch 'aktiviteter-disable-imported-edits' into aktiviteter-import