Rewrite code of MedlineImporter

[koppor]

The class org.jabref.logic.importer.fileformat.MedlineImporter uses JAXB, but can be rewritten using a StAX-Parser and thus getting rid of a JAXB dependency.

Example:

Old code:

           Object unmarshalledObject = unmarshallRoot(reader);

           // check whether we have an article set, an article, a book article or a book article set
           if (unmarshalledObject instanceof PubmedArticleSet) {
               PubmedArticleSet articleSet = (PubmedArticleSet) unmarshalledObject;
               for (Object article : articleSet.getPubmedArticleOrPubmedBookArticle()) {
                   if (article instanceof PubmedArticle) {

New code:

            XMLStreamReader xmlStreamReader = xmlInputFactory.createXMLStreamReader(reader);
            xmlStreamReader.nextTag();
            String rootElementName = xmlStreamReader.getName().getLocalPart();
            switch (rootElementName) {
                case "PubMedArticleSet":
                    ...
                    break;
               case "PubmedArticle":
                   parseArticle(xmlStreamReader, bibItems);
                   break;
               case "PubmedBookArticle":
                   parseBookArticle(xmlStreamReader, bibItems);
                   break;
               ...

[Siedlerchr]

Maybe this also allows us to solve the italic/mathml issues

[aqurilla]

Please assign this issue to me