Correct FHIRHelpers version and continue with testing CQL evaluation and QuestionnaireResponse pre-population for the Questionnaires and Libraries in CQF-US.

[dmuylwyk]

Refer to #29 / #33, and specifically this comment:

• Resolve "Test CQL evaluation and QuestionnaireResponse pre-population for the Questionnaires and Libraries in CQF-US." and "Move CQF-US README to Authoring Documentation." #33 (comment)

We should be using FHIRHelpers 4.0.1, not 4.1.0.

1. Correct FHIRHelpers version and refresh project.
2. Use $populate implementation in hapi-fhir-jpaserver-starter with Clinical Reasoning enabled.
3. To test the Questionnaires and Libraries, secure some DTR-compliant resources.
   1. Note: I've been working with the existing test resources as well as some minimally populated test resources I created myself. This appears to be sufficient for the time being. I'll revisit DTR-compliant resources when testing with $populate is working.