The import resulted in an exception if there was an array of types
instead of a string.
Both situations are now handled and API of models is kept.
Existing imported data is also kept.
- Removed individual converters for TYPO3.
Conversion is now handled in a single converter.
- The new converter will import necessary dependencies upfront, e.g.
town or organisation.
- Move import state into extra class.
Relates: #34