"Need for writing first interaction information"

Solves #639 (closed)

Writes out the

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

examples/cascade_examples/mc_conex.cpp

@@ -273,6 +273,7 @@ int main(int argc, char** argv) {
                                 longprof, observationLevel, trackCheck);
 
   output.startOfLibrary();
+
   StackType stack;
   stack.clear();