figure out ValueSets in codes.js

[seanno]

most of the valuesets for our codes just end up containing a single codesystem and that's easy. But some are more complicated, e.g.,: https://hl7.org/fhir/R4/valueset-consent-category.html ... need to figure out how to address these.

Note the current placeholder nyi code itself is a bit misleading ... we'll never get a valueset as a "system" in a codeableconcept ... we'll get one of the constituent codesystems. So the naive way to do this would be to manually break up the vs into its components and add each of them directly in the current model. Maybe that's an OK approach --- but it seems pretty brittle, would be way better to implement an "expand" approach.

Needs more thought.

[seanno]

OK --- I think I'm going to do a checkin here but leave the issue not quite resolved. The checkin: (1) removes the bogus notes about ValueSets in codes.js; (2) adds LOINC codes and does a better job with CC attribution in for this and snomed; (3) adds valueSet.js which is a loader for valuesets ... but nobody actually calls the loader as yet.

What is left to do here (for vNext) is to reconcile how/if loading valuesets should impact codes.js ... e.g., say we know that a given field uses valueset X which explicitly includes codes from system A and B. If we've already loaded system A in codes.js, no problem. But if we want to have display values for system B but it is NOT in codes.js (maybe because the value set just uses a few codes out of a very large system), do we want to somehow automate the loading of this subset? Or should we just keep valueSets and codeSystems completely separate?

A question for another day.