hasInternalSpecifier and hasExternalSpecifier should be removed unless they're needed

[gaurav]

Once upon a time, we kept the metadata for specifiers in internalSpecifiers and the OWL restrictions in hasInternalSpecifier (and ditto with external specifiers). Since specifiers are no longer OWL restrictions, we no longer need hasInternalSpecifier, and so we should get rid of it. Here's an example of it being used:

clade-ontology/phyx2owl/phyloref/Phyloreference.py

Lines 115 to 116 in df81eb6

	doc['hasInternalSpecifier'] = [specifier.as_jsonld() for specifier in self.internal_specifiers_list]
	doc['hasExternalSpecifier'] = [specifier.as_jsonld() for specifier in self.external_specifiers_list]