Check the URLs to the CERIF model elements mentioned in the schema

[jdvorak001]

As an independent command-line option, invoke the tool to validate the CERIF data model URLs (for CERIF entities and attributes) in a profile schema (+ all included schemas). Parameters: the pathname of the schema.

In analogy to #11, by default the actual URLs will be checked.

An command-line option should allow for a URL prefix to be remapped to something else. This would be used to check progressive modifications of vocabularies locally.

The tool should also raise an error if https://cerif.eurocris.org/model is seen as a URL prefix. https://w3id.org/cerif/model should be used, even if it redirects to the former one.