refactoried pathvisio module to use the new Converter class methods

pathvisio/src/main/java/lcsb/mapviewer/wikipathway/ImportExport.java

@@ -185,7 +185,7 @@ public class ImportExport implements Plugin {
 				warnings = createWarnings(appender);
 
 				CellDesignerXmlParser parser = new CellDesignerXmlParser();
-				String xml = parser.toXml(model);
+				String xml = parser.model2Xml(model);
 				PrintWriter writer = new PrintWriter(file.getPath(), "UTF-8");
 				writer.println(xml);
 				writer.close();