Added a AtomicValue distributed primitive.

Change-Id: I00ff165cbd9c6e4f2610af9877ff262527b7b048
diff --git a/core/api/src/main/java/org/onosproject/store/service/StorageService.java b/core/api/src/main/java/org/onosproject/store/service/StorageService.java
index 58ac390..9ba8780 100644
--- a/core/api/src/main/java/org/onosproject/store/service/StorageService.java
+++ b/core/api/src/main/java/org/onosproject/store/service/StorageService.java
@@ -71,6 +71,14 @@
     AtomicCounterBuilder atomicCounterBuilder();
 
     /**
+     * Creates a new AtomicValueBuilder.
+     *
+     * @param <V> atomic value type
+     * @return atomic value builder
+     */
+    <V> AtomicValueBuilder<V> atomicValueBuilder();
+
+    /**
      * Creates a new transaction context builder.
      *
      * @return a builder for a transaction context.