Renamed methods, made them more consistent and improved javadoc. This is preliminary work for a new XSL transformation feature. The methods for XSL transformation are also in "DataTransporter" namely "transformXmlStream" and "getXslStreamForXmlFile".
The "importXmlStream" method (was "executeImport") is somewhat inconsistent and should be reviewed by the core developers. The two filters "ImportXmlRootFilter" and "MagnoliaV2Filter" for the XML stream are only applied when "keepVersionHistory" ist not true, otherwise the XML stream is completely unfilterred.
The XSL transformation should happen after all filters are applied. This could be useful when bootstrapping and default values should be changed (passwords, subscribers, ...). It makes more sense to save a XSL file to version control, because it is easier to read and self-explanatory than an exported system view of the repository. Maybe a plugin mechanism for filters and transformations makes sense here.