LPS-34182 Add new ExportImportUtil and move code from DDMPortletDataHandler and JournalPortletDataHandler
LPS-34182 Add uuid and groupId to the reference and staged-model elements
LPS-34182 Refactor code to use the new uuid and groupId attributes and apply new staging patterns
LPS-34182 Apply changes to portlet data handlers
LPS-34182 Refactor content reference export
LPS-34182 Apply PortletDataContext changes to FileEntry and Folder SMDHs. New method makes easier to access reference data elements