Resolves - Add total MFD for source tree to Models serialization classes

Resolves #161 (closed)

• Add total mfd

src/main/java/gov/usgs/earthquake/nshmp/model/Models.java

@@ -15,7 +15,9 @@ import java.util.stream.Collectors;
 import com.google.gson.Gson;
 import com.google.gson.GsonBuilder;
 
+import gov.usgs.earthquake.nshmp.data.XySequence;
 import gov.usgs.earthquake.nshmp.mfd.Mfd;
+import gov.usgs.earthquake.nshmp.mfd.Mfds;
 import gov.usgs.earthquake.nshmp.model.SourceTree.Leaf;
 import gov.usgs.earthquake.nshmp.tree.Branch;
 
@@ -70,7 +72,6 @@ public class Models {
 
     // System.out.println(GSON.toJson(tree(model, 2591))); // Stonewall Ant.
     System.out.println(GSON.toJson(tree(model, 2535))); // Steens
-
   }
 
   /**
@@ -156,6 +157,7 @@ public class Models {
     final String path;
     final TectonicSetting setting;
     final SourceType type;
+    final XySequence totalMfd;
     final List<SourceBranch> branches;
 
     Tree(SourceTree tree, Path modelRoot) {
@@ -164,6 +166,8 @@ public class Models {
       this.path = modelRoot.relativize(tree.path()).toString();
       this.setting = tree.setting();
       this.type = tree.type();
+      this.totalMfd = Mfds.combine(tree.stream().map(branch -> branch.value().totalMfd())
+          .collect(Collectors.toList())).data();
 
       List<SourceBranch> branches = new ArrayList<>();