[ONOS-5897] (vCore) Create Group Manager and Store

Chages.
1. Virtual Group Manager is added
2. Virtual Group Store interface is added
3. Simple Virtual Group Store is added
4. Virtual Group Manager Test cases are added

Change-Id: I6fc1fae99f5b85fd50437b396f57f78e914ad978
diff --git a/incubator/store/src/main/java/org/onosproject/incubator/store/virtual/impl/SimpleVirtualFlowRuleStore.java b/incubator/store/src/main/java/org/onosproject/incubator/store/virtual/impl/SimpleVirtualFlowRuleStore.java
index ff13ac2..412ffd1 100644
--- a/incubator/store/src/main/java/org/onosproject/incubator/store/virtual/impl/SimpleVirtualFlowRuleStore.java
+++ b/incubator/store/src/main/java/org/onosproject/incubator/store/virtual/impl/SimpleVirtualFlowRuleStore.java
@@ -67,8 +67,11 @@
 import static org.onosproject.net.flow.FlowRuleEvent.Type.RULE_REMOVED;
 import static org.slf4j.LoggerFactory.getLogger;
 
-//TODO: support distributed flowrule store for virtual networks
+/**
+ * Manages inventory of virtual flow rules using trivial in-memory implementation.
+ */
 
+//TODO: support distributed flowrule store for virtual networks
 @Component(immediate = true)
 @Service
 public class SimpleVirtualFlowRuleStore