FI-1223: Expose multiple software versions at /version endpoint

[dehall]

Summary

Updates the /version endpoint to return a JSON containing the version numbers of both this wrapper as well as the version of the HL7 validator. Previously this was just text of the wrapper version number.
Sample result:

{"org.hl7.fhir.validation":"5.6.93","inferno-framework/fhir-validator-wrapper":"2.2.1"}

This PR replaces #42 mostly because that one was kind of a mess in terms of branch structure, but also it created a new route, and it called the wrong function to get a version number so it didn't actually return the right number for the HL7 validator.

In a few places I refer to this as "JSON containing the version numbers of software" so we could add more at some point if we want to and we don't have to rename/change docs again/etc. Though I don't have any reason to expect we'll actually need to do that.

Testing Guidance

Run the app and confirm a GET /version returns a JSON both software versions

Note there are two other changes associated with this where other tools read the version string:

• the g10 test kit changes are here: FI-1223: Support the validator /version returning a JSON onc-healthit/onc-certification-g10-test-kit#448
• the validator app changes are here: FI-1223: Parse /version endpoint returning JSON fhir-validator-app#105