Refactor User Data

[tamslo]

Refactor the ActiveDrugs class; currently, it is not really consistent in the app, when UserDate.instance.activeDrugNames is used (altough only for reading, which was the main aim) and when activeDrugs.names.

Also, activeDrugs is not reset when UserData.erase() is called (it is overwritten though upon downloading the data again, still not really clean); might be possible to tie ActiveDrugs more closely to UserData?

GenotypeResult should have extension to easily get overwritten lookup; possible to include or combine with PhenotypeInformation (handling should at least be moved to own file)?