Sorry for fixing two things in one commit.
First fixed bug is single offer and / or single price.
Those lead to exception / fatal error and are now handled.
Second fixed bug is wrong multi language handling.
Instead of using supported languages from entity (which does not exist
and was miss interpreted) we use configured system languages.
Each record is inserted with default language.
Also tourist attractions are inserted for all other languages.
They are only inserted if they have a title for that language.
Allows to import entity of type TouristAttraction.
Right now only in German, as this is most important.
Add output of tourist attraction via custom content element.
Provide first basic import mechanism.
It already allows to import entities into TYPO3 database.
Three entities are supported.
Entities are configured through import configuration.
This can be created, viewed, and edited through backend module.
Imports are tracked and accessible from backend module.
Still this is basic.
Importing lists of entities is not supported.
Multiple languages is not supported, etc.
Relates: #8214
