Implement some of the missing IPv6 flowmod treatments

Work toward ONOS-509

The following treatments are added/implemented:
  - IPV6_SRC
  - IPV6_DST
  - IPV6_FLABEL

Also:
 - Renamed L3ModificationInstruction.L3SubType.IP_SRC and IP_DST
   to IPV4_SRC and IPV4_DST (for naming consistency).
 - Few minor fixes in related code: Javadocs, comments, log messages,
   and IP address usage.

Change-Id: I551056f767a37e7cb6ae7d79f4a3929183500b57
diff --git a/core/store/serializers/src/main/java/org/onosproject/store/serializers/KryoNamespaces.java b/core/store/serializers/src/main/java/org/onosproject/store/serializers/KryoNamespaces.java
index 7c18820..cda3fda 100644
--- a/core/store/serializers/src/main/java/org/onosproject/store/serializers/KryoNamespaces.java
+++ b/core/store/serializers/src/main/java/org/onosproject/store/serializers/KryoNamespaces.java
@@ -257,6 +257,7 @@
                     L3ModificationInstruction.class,
                     L3ModificationInstruction.L3SubType.class,
                     L3ModificationInstruction.ModIPInstruction.class,
+                    L3ModificationInstruction.ModIPv6FlowLabelInstruction.class,
                     RoleInfo.class,
                     FlowRuleBatchEvent.class,
                     FlowRuleBatchEvent.Type.class,