Only populate gene to phenotype & disease to phenotype associations in phenio.db

[kevinschaper]

I think we might be having some performance problems (and unexpected API/UI behavior potentially) because genotype to phenotype associations have been getting in with the gene & disease to phenotype associations. We do want them eventually, but we need to be able to differentiate them explicitly. (It's actually possible with ZFIN IDs, less so much with MGI IDs, I think)

I'm going to update the load_sqlite script in monarch_ingest to add additional constraints.