Entity.code is not unique, code + type is unique
EntityType deletes entities on cascade
Merge remote-tracking branch 'origin/easyMetadataForModel'

Conflicts:
	DAP-System/src/main/java/org/ocha/dap/persistence/entity/curateddata/EntityType.java
	DAP-System/src/test/java/org/ocha/dap/persistence/dao/currateddata/EntityDAOImplTest.java