API: content type inherits from multi language base class
API: field definition inherits from multi language base class
API: object state inherits from multi language base class
API: fixed class documentation for ObjectState
API: object state group inherit from multi language base class
API: added field group values
API: added field group service methods to content type service
API: added field group id reference in field definition

BC: the old $fieldGroup should be treated as identifier of the field group
API: added view values
API: added view service