MedicationAdministration should not override a value set as medicationUseStatus

[cragun47]

Currently if MedicationAdministration does not have a medicationUseOccuranceDateTime, then the medicationUseStatus is overridden to unknown. If the use status is provided, it should be retained.
medicationUseOccuranceDateTime will cause a MedicationStatement to be created and it defaults to "unknown" if a medicationUseStatus is not provided. Thus a default is already accounted for.

Change code so if a medicationUseStatus is provided, it is retained.

[cragun47]

@LisaWellman FYI.

[klwhaley]

Included in release 1.1.0 https://github.com/LinuxForHealth/CsvToFHIR/releases/tag/1.1.0