State introspection

[ir4y]

• Implement #13
• Add /Questionnaire(/\d+?)/$context operation that return fhirpath context including variables and source queries to https://github.com/beda-software/aidbox-sdc
  Fhirpath debug modal should work in three modes: Questionnaire, QuestionnaireResponse, Introspection.
• For QuestionnaireResponse mode Fhirpath debug modal should only use QuestionnaireResponse as fhirData to fhirpath.evaluate.
• For Questionnaire mode Fhirpath debug modal should use Questionnaire as fhirData to fhirpath.evaluate, request context from /Questionnaire(/\d+?)/$context and pass it as context to fhirpath.evaluate.
• If fhirpath expression input in Questionnaire mode becomes empty, modal shall show all context names instead of content on the left side of the modal. Click on the name add it to fhirpath expressions input, content on the left side will be replaced by context env.
• The left side content is a value of part of fhirpath expression before first .
  For %LaunchPatient.name.first on left side should be value of %LaunchPatient