LPS-34705 rename variable as referrerStagedModel and attribute as referrerClassName
LPS-34705 Apply changes
LPS-34705 rename variable as entityStagedModel copying the pattern of entityElement
LPS-34705 Make sure we put all the referenced elements to the portlet-data.xml's but prevent double serializations
LPS-34705 Fix ExportImportUtilTest
LPS-34705 Remove never initialized parameter from PortletDataContextImpl and the deprecate old constructors