RYA-532 Assign specific interface types for Subject, Predicate, Objec…#1

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brushworth wants to merge 3 commits intoRYA-534_rdf4j_squash_2from

RYA-532_specific_interface_types_squash

Commits on Jun 30, 2020

RYA-534 Upgrade to RDF4J 3.2 and RYA-496 Upgrading to Accumulo 1.9.3
brushworth
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Commits on Jul 14, 2020

Replacing the old @Immutable annotation with @Contract(threading = ThreadingBehavior.IMMUTABLE) per the advice at https://dev-aux.com/java/org-apache-http-annotation-threadsafe-class-not-found
brushworth
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Commits on Jul 15, 2020

RYA-532 Assign specific interface types for Subject, Predicate, Object and Context and just generally clean up the code.
brushworth
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