Updated CHANGELOG.md and README.md
Modified src/validator.py as follows:
   To flag ordered lists (olo) as UnsupportedFeature instead of random bnode errors.
   To flag properties not in the ontology as unknown property
     Version 1.1 assumed an open model, where unknown properties are acceped as unconstrained.
     Version 1.2 uses a less-open model, where
          properties not in the ontology are rejected
          properties not known to the class (but known to the ontology) are accepted as constrained.

    In validator.py, replaced startswith(XSD) with startswith(str(XSD)).  This bug has already been fixed in the UCO github.
    In precondition.py, replaced len(alphabet) with len(alphabet)**prefix_length.  This is a new bug