API for exporting data to any support. The API supports File, Writer and OutputStream.

### How to export a graph file

    ExportController ec = Lookup.getDefault().lookup(ExportController.class);
    ec.exportFile(new File("export.gexf"));

### How to export to a String

    ExportController ec = Lookup.getDefault().lookup(ExportController.class);
    Exporter exporter = ec.getExporter("gexf");
    CharacterExporter characterExporter = (CharacterExporter)exporter;
    StringWriter stringWriter = new StringWriter();
    ec.exportWriter(stringWriter, characterExporter);
    String result = stringWriter.toString();