* adding --random-seed flag to help

NPLib/Core/NPOptionManager.cxx

@@ -422,7 +422,7 @@ void NPOptionManager::DisplayHelp(){
   std::cout << std::endl << "NPSimulation only:"<<std::endl;
   std::cout << "\t-M <arg>\t\t\tExecute Geant4 macro <arg> at startup" << std::endl ;
   std::cout << "\t-B <arg>\t\t\tExecute in batch mode (no ui) with Geant4 macro <arg> at startup" << std::endl ;
-
+  std::cout << "\t--random-seed <arg>\t\tSet the random generator seed to <arg> (unsigned int)" << std::endl ;
   std::cout << std::endl << std::endl ;
 
   // exit current program