Implement the Task Resource

Implement a representation of the FHIR task resource for OpenMRS that's sufficient to support a simple test order communication workflow.

At a minimum, we need to implement the values for:

• status - this should be one of `REQUESTED`, `ACCEPTED`, `REJECTED`, or `COMPLETED`
• statusReason - workflow-specific short description of the reason for the current status.
• intent - for this use case, should be set to "ORDER'
• basedOn - this should be a reference to the corresponding ServiceRequest resource
• for - this should reference the referenced Patient resource
• output - this should be a reference to the corresponding DiagnosticReport resource(s)