refactor genetic_association predicate, add association for gene to phenotype/disease association

[sierra-moxon]

From a conversation with Marc Duby from genetics provider (Translator) a few action items were identified to help clarify the model to reflect "loss of function" -> phenotype/disease associations.

• "genetic association" looks like an "association" but it is in the predicate hierarchy. Rename this to "genetically associated with", child of "associated with"
• we have two associations: "gene to phenotypic feature association" and "gene to disease association" -- we think we can combine these using "disease or phenotypic feature" mixin as a range constraint.
  • we should add the appropriate qualifiers necessary to disambiguate the gene aspect and the phenotype/disease direction.
  • disambiguate which predicate to use with a qualitative vs a quantitative phenotype/disease (e.g. which predicate to use when you need to talk about the relationship between a gene and the likelihood of getting type 2 diabetes, vs. the affect that the loss of function of a gene can have on exacerbating or ameliorating a symptom/phenotype).

Genetics provider uses "BMI" as a "phenotype" instead of a measurement of obesity or some other disease. Some discussion of this would be helpful at a DM call.