ability to transform config files using XSL stylesheets prior to parsing. done after xincludes are resolved. use the standard xsl way of adding a processing instruction in the document that should be transformed, e.g. <?xml-stylesheet type="text/xml" href="%core.config_dir%/test.xsl"?> after the xml prolog and before the document element. refs #509 (ability to embed stylsheets in the same document is missing, see #508