[ONOS-4753] Identity/identityref implementation and UT

Change-Id: I40148fa228465555be3bdf410cc294ffc0f34c18
diff --git a/plugin/src/test/resources/interfileidentityimportdependency/featurefile1.yang b/plugin/src/test/resources/interfileidentityimportdependency/featurefile1.yang
new file mode 100644
index 0000000..b808b11
--- /dev/null
+++ b/plugin/src/test/resources/interfileidentityimportdependency/featurefile1.yang
@@ -0,0 +1,30 @@
+module syslog1 {
+    yang-version 1;
+    namespace "http://huawei1.com";
+    prefix "sys1";
+
+    import "syslog2" {
+       prefix "sys2";
+    }
+
+    identity ipv4-address-family {
+       base sys2:ref-address-family;
+    }
+
+    identity ipv6-address-family {
+       base sys2:ref-address-family;
+    }
+
+    leaf tunnel {
+        type identityref {
+            base sys2:ref-address-family;
+        }
+    }
+
+    leaf-list network-ref {
+        type identityref {
+            base sys2:ref-address-family;
+        }
+    }
+
+}