Added option to generate ISOXML taskmap, added missing Nbs data

FarmmapsNbs/Models/TargetNData.cs

@@ -0,0 +1,9 @@
+namespace FarmmapsNbs.Models
+{
+    public class TargetNData
+    {
+        public double TSum { get; set; }
+        public int TargetYield { get; set; }
+        public double TargetN { get; set; }
+    }
+}