fix failing test: id property is required in Grails also for classes with composite id
Merge branch '3.x'

Conflicts:
	grails-datastore-gorm-hibernate/src/test/groovy/org/codehaus/groovy/grails/orm/hibernate/CompositeIdentifierWithAssociationsTests.groovy
	grails-datastore-gorm-hibernate4/src/test/groovy/org/codehaus/groovy/grails/orm/hibernate/CompositeIdentifierWithAssociationsTests.groovy