remove optional folderish profile
check for IDexterityContent instead of meta_type
use custom class for testing migration to wor around change to folderish
fix syntax
allow to pass the klass-names and allow migration with the same klass
Harden test for itemish/folderish. Allow to force folderish_migration by passing migrate_to_folderish=True
allow to force migrate_to_folderish from the BaseClassMigratorForm