✨ Profile phenotype

[torstees]

This PR adds:

• an "ncpi-phenotype" StructureDefinition;
• ValueSets; and
  • "phenotype-codes" (HPO) for Observatrion.code;
  • "phenotype-observation-codes" (SNOMED CT clinically present/absent) for Observation.valueCodeableConept; and
  • "phenotype-interpretation" for Observation.interpretation;
• an example Observation resource

This PR closes #34.

[liberaliscomputing]

@torstees

The changes look great. If we want to contextualize the use of the value sets within our phenotype profile, I recommend to name:

• "observation-interpretation" >> "phenotype-interpretation"
• "observation-type-codes" >> "phenotype-observation-codes"

And could you recheck the indentation of the "snomed-ct" code system?