Optimize AxiomTranslator#containsONTObject(..) and AxiomTranslator#findONTObject(..) for the case of named triple

[sszuev]

If subject and object are URIs then there is no need to iterate for searching.

This is an optimization for the direct mode (i.e. when cache is disabled).
And it is, probably, the last thing for the 2.1.0 release

Update: add simplified contains/find for the case if the subject and object are anonymous individuals - since they are unique within the system and does not require complex hashCode/equlas.

For a case when triples has one anonymous expression (as subject or object), the optimization is also needed, but this can be next issue.

[sszuev]

rdfs:subPropertyOf: 4bd932f

[sszuev]

There are following axiom types unhandled:

• DisjointUnion
• SubPropertyChainOf
• HasKey
• NegativeObjectPropertyAssertion
• NegativeDataPropertyAssertion
• Rule

there are no named main triple for these axioms;
also all of them are rare - i.e. standard searching would be efficient, no need any optimization.

done