Add a factory class to generate FormularyDrug (MedicationKnowledge) data

[vanessuniq]

Add the following optional fields to the FormularyDrug (MedicationKnowledge resource) class generator:

• Add support for associatedMedication field
• Add support for relatedMedicationKnowledge field
• Add support for medecineClassification field

This would great for testing, allowing a client to lookup alternative medications in a formulary.