New output format for interaction histogram and simplifications

• with boost::histogram 1.74 things got simpler and the workaround treatment of nuclear projectiles is obsolete now (see https://github.com/boostorg/histogram/issues/279)
• no custom text output anymore, save_hist() is used now insted to save npz files.

Documentation/Examples/vertical_EAS.cc

@@ -252,11 +252,8 @@ int main(int argc, char** argv) {
   auto const hists = sibyllCounted.GetHistogram() + sibyllNucCounted.GetHistogram() +
                      urqmdCounted.GetHistogram() + proposalCounted.GetHistogram();
 
-  hists.saveLab("inthist_lab.txt");
-  hists.saveCMS("inthist_cms.txt");
-
-  hists.saveLab("inthist_lab.txt");
-  hists.saveCMS("inthist_cms.txt");
+  hists.saveLab("inthist_lab.npz");
+  hists.saveCMS("inthist_cms.npz");
 
   longprof.save("longprof.txt");