Introduce new Condition domain object, backed by a new `condition` table

Introduce new Condition domain object, backed by a new `condition` table:

class Condition extends BaseOpenmrsData {
  CodedOrFreeText condition; // required
  ConditionClinicalStatus clinicalStatus; // required
  ConditionVerificationStatus verificationStatus; // optional
  Condition previousVersion; // optional
  String additionalDetail; // optional, a short comment, maps to https://www.hl7.org/fhir/condition-definitions.html#Condition.note
  Date onsetDate; // optional
}

Most of the work on this ticket is done. What is remaining is discussed on the talk link above. In summary, the openmrs-core table should be named "conditions", a name already taken by the emrapi module. We therefore need a solution which will rename the emrapi module table to something like emrapi_conditions, but without breaking clients who are not yet running platform 2.2
Iheanyichukwu Kelechi raised a pull request which needs to be tested and have any resulting problems fixed.
When this is done, the work which was done for TRUNK-5360 needs to reflect the new condition table names in both openmrs-core and the emrapi module. An attempt has so far been made at https://github.com/openmrs/openmrs-core/pull/2662