Implementation of $apply API

[fredhersch]

User story:
As an implementer I can use the $apply operation to generate a CarePlan for a patient given a PlanDefinition

Background
CQL (Clinical Quality Language) is the HL7 standard for providing logic execution for decision support and clinical quality measures.

Our initial goal with the CQL Library will be to demonstrate over time the ability to:

• Generate a MeasureReport via $measure-evaluate operation
• Load and execute a custom CQL library (Library resource) for decision logic
• Transform a PlanDefinition to a CarePlan using $apply operation

[jingtang10]

dependencies:

• Support JSON as a serialization format for ModelInfo cqframework/clinical_quality_language#640
• Annotation serialization with JXSON cqframework/clinical_quality_language#523