Add plate well concentrations to output data

src/main/java/Plate.java

@@ -32,7 +32,7 @@ public class Plate {
         for (List<Integer[]> w: wells) {
             concentrations.add(w.size());
         }
-        concentrations.toArray(this.concentrations);
+        this.concentrations = concentrations.toArray(new Integer[concentrations.size()]);
     }
 
     public void fillWellsExponential(String sourceFileName, List<Integer[]> cells, double lambda){