Update the Test Suite

[bergos]

I've added some tests to shacl-engine for some bugs found in my implementation. Others may have run into similar issues. It would be useful to have a new, extended test suite with a bigger coverage of the specification.

[ajnelson-nist]

I've also found some corner cases that weren't entirely clear from the specification, and would welcome the opportunity to get them imported into a test suite update.

[VladimirAlexiev]

• protect from cyclical sh:path #165 asks for a test with cyclical path
• conformance testing of modern SHACL implementations #203 asks for a testing facility. I know that's not the job of the WG, but any collected info will be appreciated