Add support for `sh:TripleTerm` to `sh:nodeKind` and allow lists

[bergos]

sh:nodeKind should be extended to support sh:TripleTerm. List values should be accepted, like in the recent change for sh:datatype and sh:class in PR #395, to avoid extending the list of possible values with all combinations.

[HolgerKnublauch]

Are there any real-world scenarios where a node can be either TripleTerm or something else?

[ajnelson-nist]

Are there any real-world scenarios where a node can be either TripleTerm or something else?

What about a TripleTerm or the IRI or BNode that identifies a TripleTerm? I.e., just not a Literal.

[bergos]

Are there any real-world scenarios where a node can be either TripleTerm or something else?

There should be only one use case: checking if a triple term is used with the intended property rdf:reifies. But the specification defines it only with SHOULD and allows other use cases.