We have many version of num_arguments for the DCmd subclasses. They all have identical structure. We should templatize them to reduce duplicated code and avoid cut-and-paste errors.

Examples:

int ThreadDumpDCmd::num_arguments() {
  ResourceMark rm;
  ThreadDumpDCmd* dcmd = new ThreadDumpDCmd(NULL, false);
  if (dcmd != NULL) {
    DCmdMark mark(dcmd);
    return dcmd->_dcmdparser.num_arguments();
  } else {
    return 0;
  }
}

int JMXStartRemoteDCmd::num_arguments() {
  ResourceMark rm;
  JMXStartRemoteDCmd* dcmd = new JMXStartRemoteDCmd(NULL, false);
  if (dcmd != NULL) {
    DCmdMark mark(dcmd);
    return dcmd->_dcmdparser.num_arguments();
  } else {
    return 0;
  }
}