resolved jena-backed namespaces for expr validator
resolved jena-backed namespaces for expr validator

fixes 500 error with endpoint /expressions/{bel}/validation

OpenBEL/openbel-api,OpenBEL/openbel-api,OpenBEL/openbel-server,OpenBEL/openbel-server,OpenBEL/openbel-api,OpenBEL/openbel-api,OpenBEL/openbel-server