Support export of OpenMRS data using a FHIR Condition Resource

We need to support the export of OpenMRS data using the FHIR Condition resource [0]. Traditionally, OpenMRS has stored Conditions as OpenMRS observations. However, this may change in the future, and a separate condition table may be introduced. Therefore, developing support to manage Conditions includes developing a strategy pattern, as used for working with OpenMRS allergies.

[0] http://hl7-fhir.github.io/condition.html