LPS-33626 Move portlet-data.xml creation to portlet data context
LPS-33626 Use new context based root element for portlet-data.xml in BasePortletDataHandler
LPS-33626 Cleaning up doExportData and doImportData methods
LPS-33626 Moving data validation to a new method so implementing portlet data handlers can override/use
LPS-33626 Apply changes - new pattern to JournalContentPortletDataHandler as example
LPS-33626 Apply same pattern to all portlet data handlers
LPS-33626 Fixing PageRatingsPortletDataHandler to produce a proper xml file otherwise it won't be possible to import
LPS-33626 Adding missing null checks