TRUNK-4443 Renaming start_date in order to date_activated

(cherry picked from commit cc8882cdaa734ee3fce8025775b8529a88aa16ab)

Conflicts:
	api/src/main/java/org/openmrs/api/db/hibernate/HibernatePatientSetDAO.java
	api/src/main/java/org/openmrs/reporting/export/DataExportFunctions.java
	api/src/main/resources/liquibase-update-to-latest.xml
	api/src/test/resources/org/openmrs/api/include/EncounterServiceTest-initialData.xml
	api/src/test/resources/org/openmrs/api/include/OrderServiceTest-ordersList.xml
	api/src/test/resources/org/openmrs/include/standardTestDataset.xml
	webapp/src/main/webapp/WEB-INF/messages.properties
TRUNK-4443 Fixed failing integration tests

(cherry picked from commit ee12c7cd1881efdcef737d27740123f32af5a901)