HV-844 Making the validator version used in TCK run configurable
HV-850 Making junit.framework.* an illegal import in checkstyle configuration
HV-589 Introducing UnconstrainedEntityMetaDataSingleton as a placeholder for unconstrained types.

This placeholder is used when BeanMetaDataManager#isConstrained is called. When retrieving an instance of BeanMetaData always a proper BeanMetaDataImpl instance is returned.