Cms npi fix

*Parsed npis to identifier format.
* Added more comments to explain thought process
* instead of having two fields for prescriber and provider, they were simplified into performer with type attribute specifying what kind of performer they were.
* Had to modify schema in performer so that it could take either cda_name or a generic name string, since ccda sample files also tend to use a simple string for names, and people's name as well.