Changed Drug.drugReferenceMaps and orderType.conceptClasses to LinkedHashsets
TRUNK-4279:  Add DrugValidator and validate drugReferenceMaps from it
Follow up to Add DrugValidator and validate drugReferenceMaps from it - TRUNK-4279
TRUNK-4311 Concept class can only be mapped to exactly one order type
Follow up to Add OrderTypeValidator - TRUNK-4311
Added unique constraints to care_setting.name, order_type.name and order_frequency.concept_id
Follow up to fix failing unit tests
Fixed faulty not null constraints in Order.hbm.xml and updated the existing test data and methods

Fixed failing tests
Refactor OrderService.getOrders- TRUNK-4173