(SHACL) Validating RDF data using SHACL

We will make use of the UserShape example in SHACL from the Validating RDF Data book to demonstrate tha capabilities of the SHACL validator we propose.

In case we want to perform the SHACL validation, it's as easy as executing the shacl-validate command provided a shapes and data graph. According to this, an RDF graph conforming to the example above is:

cargo run -- shacl-validate --shapes examples/book.ttl --data examples/book_conformant.ttl

cargo run -- shacl-validate --shapes examples/book.ttl --data examples/book_non-conformant.ttl