Add DSTU3 Support To UploadTerminologyCommand

[KevinDougan]

Currently, if you try and run the UploadTerminologyCommand with a DSTU3 terminology file, you will see an Exception:

2021-07-19 14:19:35.302 [main] ERROR ca.uhn.fhir.cli.App Error during execution: ca.uhn.fhir.context.ConfigurationException: This context is for FHIR version "DSTU3" but the class "org.hl7.fhir.r4.model.CodeSystem" is for version "R4"
at ca.uhn.fhir.context.RuntimeResourceDefinition.<init>(RuntimeResourceDefinition.java:67)
at ca.uhn.fhir.context.ModelScanner.scanResource(ModelScanner.java:335)at ca.uhn.fhir.context.ModelScanner.scan(ModelScanner.java:186)
at ca.uhn.fhir.context.ModelScanner.init(ModelScanner.java:135)
at ca.uhn.fhir.context.ModelScanner.<init>(ModelScanner.java:94)
at ca.uhn.fhir.context.FhirContext.scanResourceTypes(FhirContext.java:880)
at ca.uhn.fhir.context.FhirContext.scanResourceType(FhirContext.java:866)
at ca.uhn.fhir.context.FhirContext.getResourceDefinition(FhirContext.java:428)
at ca.uhn.fhir.parser.BaseParser.parseResource(BaseParser.java:746)
at ca.uhn.fhir.parser.BaseParser.parseResource(BaseParser.java:798)
at ca.uhn.fhir.cli.UploadTerminologyCommand.invokeOperation(UploadTerminologyCommand.java:167)
at ca.uhn.fhir.cli.UploadTerminologyCommand.run(UploadTerminologyCommand.java:113)
at ca.uhn.fhir.cli.BaseApp.run(BaseApp.java:267)
at ca.cdr.cli.App.main(App.java:70)

The purpose of this issue is to add support for DSTU3 terminology file uploads.