MemPOI - Adding bundled NumberSumSubFooter to the export

MemPOIBundledSubFooter.java

try {

  // creates MemPOI using its builder and requests the export
  MempoiBuilder.aMemPOI()
    .withWorkbook(new SXSSFWorkbook())
    .addMempoiSheet(new MempoiSheet(prepStmt))
    .withStyleTemplate(new ForestStyleTemplate())
    .withMempoiSubFooter(new NumberSumSubFooter())
    .build()
    .prepareMempoiReportToByteArray()
    .get();

} catch (ExecutionException e) {
  System.out.println(e.getCause().getMessage());
} catch (InterruptedException e) {
  e.printStackTrace();
}