Add SDK support for FHIRPath Math operations for FHIR Specification R4B

[allan-on]

Is your feature request related to a problem? Please describe.
The R4 FHIR spec version supported by the SDK includes an FHIRPath spec version that doesn't have support for Math functions like .exp(), .power(), .abs()... that can be used in FHIRPath expressions for computations such as (%weight/(%height.power(2))).round(1).

Describe the solution you'd like
Support for Math functions should be added by adding implementation of the operations that aren't supported in the FHIRPath Spec.

Describe alternatives you've considered
Some of the alternatives we've considered include:

• Upgrading to a much more recent FHIR Spec version that supports FHIRPath Math functions e.g. R5
• Delegating of computations that require the math functions to a Service class in the app that can be invoked (probably during post-processing of the QuestionnaireResponse?)

Additional context
See FHIRPath Specification: Publication (Version) History

Would you like to work on the issue?
Yes

[allan-on]

This has been addressed in FHIR Engine 0.1.0 beta05 Pre-release
🙌🏾