Some installations might need to add further images
to records imported from ThüCAT.
The records are now extended to support adding images by editors.
The images are not touched during import.
The images are also ignored during clean ups,
the editor is in full control.
This feature for now is only added to tourist attractions by default.
The feature is implemented in a way that all objects extending the
``WerkraumMedia\ThueCat\Domain\Model\Frontend\Base`` class are usable
by adding an ``editorial_images`` field to their table.
This should ensure rendering works as expected.
Most important: This ensures data is available in frontend templates.
Add dev dependency to fluid_styled_content. This is necessary to test
our rendering integration with fluid_styled_content defaults.
Relates: #34
