have jac_cell use species names in output instead of indices

this makes it easier to understand

Author: zingale

unit_test/jac_cell/jac_cell.H

@@ -66,8 +66,10 @@ void jac_cell_c()
     // output
 
     for (int ii = 1; ii <= neqs; ++ii) {
+        std::string ilabel = (ii < neqs) ? short_spec_names_cxx[ii-1] : "e";
         for (int jj = 1; jj <= neqs; ++jj) {
-            std::cout << "J(" << std::setw(3) << ii << ", " << std::setw(3) << jj << ") = "
+            std::string jlabel = (jj < neqs) ? short_spec_names_cxx[jj-1] : "e";
+            std::cout << "J(" << std::setw(4) << ilabel << ", " << std::setw(4) << jlabel << ") = "
                       << std::setw(20) << jac_numerical(ii,jj) << " "
                       << std::setw(20) << jac_analytic(ii,jj) << std::endl;
         }