Introduce an Enum for "condition status"

Introduce an Enum for what we've historically called "condition status" and FHIR refers to as ConditionClinicalStatus (https://www.hl7.org/fhir/valueset-condition-clinical.html). We support a subset of the FHIR statuses, and we support one additional status not included in FHIR:

enum ConditionClinicalStatus {
    ACTIVE,
    INACTIVE,
    HISTORY_OF // this maps most closely to the "remission" status in FHIR, but we want to be more clear about the common OpenMRS use case
}