[ONOS-4753] Identity/identityref implementation and UT

Change-Id: I40148fa228465555be3bdf410cc294ffc0f34c18
diff --git a/plugin/src/test/resources/interfileidentityinlude/IdentityInModule.yang b/plugin/src/test/resources/interfileidentityinlude/IdentityInModule.yang
new file mode 100644
index 0000000..e42ad86
--- /dev/null
+++ b/plugin/src/test/resources/interfileidentityinlude/IdentityInModule.yang
@@ -0,0 +1,27 @@
+module syslog3 {
+     yang-version 1;
+     namespace "http://huawei3.com";
+     prefix "sys3";
+
+     include "syslog4";
+
+     identity ipv4-address-family {
+         base ref-address-family;
+     }
+
+     identity ipv6-address-family {
+         base ref-address-family;
+     }
+
+    leaf tunnel {
+         type identityref {
+             base ref-address-family;
+         }
+    }
+
+    leaf-list network-ref {
+        type identityref {
+            base ref-address-family;
+        }
+    }
+}