BeReferralPrescription - Put "replaces" field in "Must support"

[SmalsJulien]

When a prescription is created based on an expired prescription, UHMEP will use this field in the new prescription to give the reference of the expired prescription.

[Mcobbaert]

This functionality needs to be described in the business rules document - cookbook. Is not part of Fhir.
We use "based on" instead of "replaces" already included in the "must support".

[bdc-ehealth]

@Mcobbaert @annenerenhausen , I think @SmalsJulien is right. From a semantic interoperability view, the reference to the expired request should be in the ServiceRequest.replaces (https://hl7.org/fhir/R4/servicerequest-definitions.html#ServiceRequest.replaces).

[bdc-ehealth]

WG: solved in #47