Work toward common IP address classes.

 * Updated classes PortAddresses (in core/api) and Interface (in sdnip)
   to use class InterfaceIpAddress instead of IpPrefix
 * Updated corresponding unit tests and relevant code
 * Minor refactoring inside ProxyArpManager to simplify some of the
   logic and usage related to PortAddresses. Also, renamed
   method findOutsidePortInSubnet() to findPortInSubnet() and updated
   its implementation to reflect better its usage.
diff --git a/core/store/trivial/src/main/java/org/onlab/onos/store/trivial/impl/SimpleHostStore.java b/core/store/trivial/src/main/java/org/onlab/onos/store/trivial/impl/SimpleHostStore.java
index ee8570d..f28e656 100644
--- a/core/store/trivial/src/main/java/org/onlab/onos/store/trivial/impl/SimpleHostStore.java
+++ b/core/store/trivial/src/main/java/org/onlab/onos/store/trivial/impl/SimpleHostStore.java
@@ -19,6 +19,7 @@
 import org.onlab.onos.net.host.HostEvent;
 import org.onlab.onos.net.host.HostStore;
 import org.onlab.onos.net.host.HostStoreDelegate;
+import org.onlab.onos.net.host.InterfaceIpAddress;
 import org.onlab.onos.net.host.PortAddresses;
 import org.onlab.onos.net.provider.ProviderId;
 import org.onlab.onos.store.AbstractStore;
@@ -202,8 +203,9 @@
             if (existing == null) {
                 portAddresses.put(addresses.connectPoint(), addresses);
             } else {
-                Set<IpPrefix> union = Sets.union(existing.ips(), addresses.ips())
-                        .immutableCopy();
+                Set<InterfaceIpAddress> union =
+                    Sets.union(existing.ipAddresses(),
+                               addresses.ipAddresses()).immutableCopy();
 
                 MacAddress newMac = (addresses.mac() == null) ? existing.mac()
                         : addresses.mac();
@@ -221,8 +223,9 @@
         synchronized (portAddresses) {
             PortAddresses existing = portAddresses.get(addresses.connectPoint());
             if (existing != null) {
-                Set<IpPrefix> difference =
-                        Sets.difference(existing.ips(), addresses.ips()).immutableCopy();
+                Set<InterfaceIpAddress> difference =
+                        Sets.difference(existing.ipAddresses(),
+                                        addresses.ipAddresses()).immutableCopy();
 
                 // If they removed the existing mac, set the new mac to null.
                 // Otherwise, keep the existing mac.