Handling of datamodel errors while crawling

This MR will add output on missing record types and/or properties that are found while crawling.

Focus on datamodel_problems.py and cfood.py.

Can be tested with test_datamodel_problems.py in integrationtests/single_tests for datamodel_problems.py only and test_crawl_with_datamodel_problems.py in integrationtests/full_tests for a crawler with a broken data model. Both tests are used in the test environment from the README_SETUP.md and can simply be executed with pytest.