Adding support for VLAN_PUSH with EtherType (incl. Q-in-Q)

 - Allowing VLAN_PUSH Instruction to use ethernetType (incl. using REST API)
 - Adding QINQ (0x88a8) Ethernet type
 - Updating InstructionCodec decoders/encoders
 - Updating TrafficTreatment/FlowEntryBuilder

Change-Id: I723cc936a8a49c39da9abe65ba9e5b1bdc1392bf
diff --git a/core/api/src/main/java/org/onosproject/net/flow/DefaultTrafficTreatment.java b/core/api/src/main/java/org/onosproject/net/flow/DefaultTrafficTreatment.java
index fbe240a..623ece1 100644
--- a/core/api/src/main/java/org/onosproject/net/flow/DefaultTrafficTreatment.java
+++ b/core/api/src/main/java/org/onosproject/net/flow/DefaultTrafficTreatment.java
@@ -401,6 +401,11 @@
         }
 
         @Override
+        public Builder pushVlan(EthType ethType) {
+            return add(Instructions.pushVlan(ethType));
+        }
+
+        @Override
         public Builder transition(Integer tableId) {
             return add(Instructions.transition(tableId));
         }