Vector cost proposed to TST on 2016-07-13

First part implemented: weight interface introduced and integrated, default weight implementation added.

Change-Id: Ia46f1b44139069aa171a3c13faf168351bd7cc56
diff --git a/utils/misc/src/main/java/org/onlab/graph/DefaultMutablePath.java b/utils/misc/src/main/java/org/onlab/graph/DefaultMutablePath.java
index b6c5e38..c8f8f86 100644
--- a/utils/misc/src/main/java/org/onlab/graph/DefaultMutablePath.java
+++ b/utils/misc/src/main/java/org/onlab/graph/DefaultMutablePath.java
@@ -31,7 +31,7 @@
 public class DefaultMutablePath<V extends Vertex, E extends Edge<V>> implements MutablePath<V, E> {
 
     private final List<E> edges = new ArrayList<>();
-    private double cost = 0.0;
+    private Weight cost;
 
     /**
      * Creates a new empty path.
@@ -61,7 +61,7 @@
     }
 
     @Override
-    public double cost() {
+    public Weight cost() {
         return cost;
     }
 
@@ -71,7 +71,7 @@
     }
 
     @Override
-    public void setCost(double cost) {
+    public void setCost(Weight cost) {
         this.cost = cost;
     }