Frequency

[pnrobinson]

I am extending Dan's item on frequency from #13

• Support an inline micro-ontology (or GOLR if possible) for terms under Frequency http://compbio.charite.de/hpoweb/showterm?id=HP:0040279. Since Frequency only has a single column, we will use the canonical name for HPO, rather than ID. See http://compbio.charite.de/hpoweb/showterm?id=HP:0040284 where 'very rare' should be stored.
• Also allow frequency data in the form of 5/17 (e.g., a study in whichb 5 of 17 patients had some HPO term) or 33%