Implemented FHIR R5, version 5.0.0

[marcovisserFurore]

Description

Implemented FHIR R5, version 5.0.0

To be discussed:

• ConstraintSeverity (http://hl7.org/fhir/ValueSet/constraint-severity) (in Hl7.Fhir.Conformance) is moved from namespace Hl7.Fhir.Model to Hl7.Fhir.Model.ElementDefinition. Breaking change?
• specification.zip is partly made by DownloadFhirBuildProfile.ps1. After generation I replaced extension-definitions.xml by a folder extensions with the content of the package hl7.fhir.uv.extensions.r5#1.0.0.tgz. Should we automate this process?
• Script DownloadFhirBuildProfile.ps1 downloaded the careplan example and moved it to folder src\Hl7.Fhir.Specification.R5.Tests\TestData\validation\careplan-example-integrated.xml. This example was not correct and I manually downloaded the example from https://www.hl7.org/fhir/careplan.html. Should we automate this?
• ele-1 is not in the condition of Element anymore for R5. Is that correct?
• The following elements are getting a IsSummary attribute, while the definition does not define that:
  • ConceptMap.group.element.target.relationship
  • Contract.term.action.doNotPerform
  • List.entry.deleted
  • Questionnaire.item.enableWhen
    According to Gino this is implemented in codegen because of this JIRA issue. I made a change in codegen to have the old behavior back. Should we add a Jira ticket for that?

Result:

• ConstraintSeverity has been moved back to namespace Hl7.Fhir.Model to prevent breaking changes
• DownloadFhirBuildProfile.ps1 has been adjusted so that it downloads the extension package automatically and merge it into specification.zip.
• The removal of condition ele-1 in Element is correct.

Related issues

Resolves #2418

FirelyTeam Checklist

• Update the title of the PR to be succinct and less than 50 characters
• Mark the PR with the label breaking change when this PR introduces breaking changes