Support component-based stratifiers

[brynrhodes]

The R4 Measure and MeasureReport resources introduced the ability to represent stratifiers as components:

https://github.com/HL7/fhir/blob/master/source/measure/measure-hiv-indicators.xml#L100

Add support for stratification using components.

This is related to work with the WHO on representing HIV indicators

The specification for multi-component stratification is here:
https://hl7.org/fhir/measure-definitions.html#Measure.group.stratifier.component

The code that implements stratifier support is here:
https://github.com/cqframework/clinical-reasoning/blob/master/evaluator.measure/src/main/java/org/opencds/cqf/cql/evaluator/measure/common/MeasureEvaluator.java#L378

For multi-component stratifiers, two subjects are grouped into the same stratification if all of the components are equal. IOW, if a multi-component stratifer has Age and Gender, two subjects are grouped together if they are both 18 and Male. Someone 17 and Male, or 18 and Female would not be in the same stratification.

Acceptance Criteria:
The multi-component measure (or an analog) is added as a test case to the CR repository and the tests pass.

[litlfred]

This is critical work. Thanks!