Integrate with https://fhirpath-lab.com/FhirPath

[ir4y]

https://github.com/brianpos/fhirpath-lab/blob/develop/server-api.md

[ir4y]

Some comments from Brian Postlethwaite

These are the logical models for what data is in/out of the custom operation Simplified logical models for what data in the request/response.

But represented using fhir parameters resources. I'm trying to get real profiles for these to go with things too. The Abstract Syntax tree format isn't documented anywhere. I built it from the Firely engine, and mapped the fhirpath.js to that. In progress mapping the HAPI engine to it too. The tricky part is making it work with the "invert tree" format to make it more readable.