Support for edges using an annotation property

[gouttegd]

KGCL-Java currently only supports two types of edges:

• direct classification, where the predicate is rdfs:subClassOf (yields a subject SubClassOf: object axiom);
• existential restriction, where the predicate is an object property (yields a subject SubClassOf: <predicate> some object axiom).

In KGCL, an edge can also use an annotation property (provided that the value is an IRI and not a literal – if the value is a literal, then we’re talking about a node annotation rather than an edge), and should yield an annotation assertion axiom.

from obophenotype/cell-ontology#2298