Improve handling of curly bracket entries from OMIM

[jxchong]

Disease ID and Name
Example https://omim.org/entry/260500 {Choroid plexus papilloma}

Further information (Frequency, Onset, Pubmed-references, Comments)
Per OMIM, braces, "{ }", indicate mutations that contribute to susceptibility to multifactorial disorders (e.g., diabetes, asthma) or to susceptibility to infection (e.g., malaria).

Right now this HPO entry (and I suspect many other disease entities in HPO for other {} diseases) do not have this multifactorial relationship documented. I suggest adding Non-Mendelian inheritance HP:0001426 or and/or more specifically, Polygenic inheritance HP:0010982 to all of these entries to reflect the fact that they are not Mendelian diseases.