[CORD-458] Updates ARP handler

Changes:
- SR application uses NRM;
- Adds hooks for ND protocol;
- Updates ARP handler to better leverage on NRM;
- Reworks to take into account IPv4/IPv6 together;

Change-Id: Iab55b8c5ef7d973928d8ad47e2c2a482fb9c5c8a
diff --git a/src/main/java/org/onosproject/segmentrouting/SegmentRoutingService.java b/src/main/java/org/onosproject/segmentrouting/SegmentRoutingService.java
index 7375b98..6f4b4e6 100644
--- a/src/main/java/org/onosproject/segmentrouting/SegmentRoutingService.java
+++ b/src/main/java/org/onosproject/segmentrouting/SegmentRoutingService.java
@@ -15,7 +15,7 @@
  */
 package org.onosproject.segmentrouting;
 
-import org.onlab.packet.Ip4Prefix;
+import org.onlab.packet.IpPrefix;
 import org.onosproject.net.DeviceId;
 
 import java.util.List;
@@ -115,5 +115,5 @@
      *
      * @return device-subnet mapping
      */
-    Map<DeviceId, Set<Ip4Prefix>> getDeviceSubnetMap();
+    Map<DeviceId, Set<IpPrefix>> getDeviceSubnetMap();
 }