Validator
* fix NPE bug logging terminology server calls
* fix NPE bug validating logical models
* fix problem with Type Name when validating against Logical Models
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Validator:
* Hack around erroneous R3 Invariant (ref-1)
* Add support for generating terminology spreadsheets from the command line validator
* Validate Resource.id and Element.id properly
Other Code Changes:
* Change the FHIRPath interface IEvaluationContext.resolveConstant to return List<Base> not Base (BREAKING CHANGE!)
* Binary Resource Renderer
* Spreadsheet Generation for terminology resources (org.hl7.fhir.r5.renderers.spreadsheets package)
* Fix various NPEs discovered by users
* Fix rendering of value sets that have no definition
* Mark generated narrative with a flag in user data
* return system for display when IWorkerContext.validateCode is called
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* Differential element fields minValue/maxValue are now correctly treated in the snapshot generation process
* Conversion context added to conversions process
* Users can now define custom behavior for CodeSystems, Extensions, BundleEntries, and Types by extending BaseAdvisor.
* Resource Conversions are now thread-safe, each using their own instance of the conversion context that is unique
* ConversionFactory classes are statically accessed, to minimize changes downstream
* I need to add more tests, there were very few to begin with, and it's my next task
* All conversion libraries and no play makes Mark a dull boy
* Exposed showMessagesFromReferences on the command line interface to support reporting validation errors on referenced types (particularly useful when validating messages & documents)
* https://github.com/hapifhir/org.hl7.fhir.core/issues/564
* https://github.com/hapifhir/org.hl7.fhir.core/issues/513
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