fix: Virtual flow rule and packet store

Changes.
1. Simple Packet store is declared as OSGi component
2. some description is added

Change-Id: Iaffa6786bbca5b967926b19183f45b723b8ab211
diff --git a/incubator/api/src/main/java/org/onosproject/incubator/net/virtual/VirtualNetworkService.java b/incubator/api/src/main/java/org/onosproject/incubator/net/virtual/VirtualNetworkService.java
index 06d164c..1c05a2b 100644
--- a/incubator/api/src/main/java/org/onosproject/incubator/net/virtual/VirtualNetworkService.java
+++ b/incubator/api/src/main/java/org/onosproject/incubator/net/virtual/VirtualNetworkService.java
@@ -124,6 +124,7 @@
      * <li>{@link org.onosproject.net.host.HostService}</li>
      * <li>{@link org.onosproject.net.topology.TopologyService}</li>
      * <li>{@link org.onosproject.net.topology.PathService}</li>
+     * <li>{@link org.onosproject.net.packet.PacketService}</li>
      * <li>{@link org.onosproject.net.flow.FlowRuleService}</li>
      * <li>{@link org.onosproject.net.flowobjective.FlowObjectiveService}</li>
      * <li>{@link org.onosproject.net.intent.IntentService}</li>