"Need for writing first interaction information"

Solves #639 (closed)

Writes out the

• pdg ID
• position
• momentum vector
• time
• dX

applications/c8_air_shower.cpp

@@ -220,8 +220,7 @@ int main(int argc, char** argv) {
                "Force the location of the first interaction.")
       ->group("Misc.");
   bool force_decay = false;
-  app.add_flag("--force-decay", force_decay,
-               "Force the primary to immediately decay")
+  app.add_flag("--force-decay", force_decay, "Force the primary to immediately decay")
       ->group("Misc.");
   bool disable_interaction_hists = false;
   app.add_flag("--disable-interaction-histograms", disable_interaction_hists,