ONOS-7050 Refactored PI translation service and store

The translation store is now able to maintain mappings between
translated entities and specific instances of a PI entry in the network
(i.e. applied to a device).

The translation service has been refactored to allow users to
learn and forget translated entities.

The refactoring of the P4Runtime driver using this service will be
submitted separatelly.

Change-Id: Iaafd87d90232514853ca0dea0115dbae4f6e7886
diff --git a/core/api/src/main/java/org/onosproject/net/pi/service/PiGroupTranslator.java b/core/api/src/main/java/org/onosproject/net/pi/service/PiGroupTranslator.java
new file mode 100644
index 0000000..d5eb5af
--- /dev/null
+++ b/core/api/src/main/java/org/onosproject/net/pi/service/PiGroupTranslator.java
@@ -0,0 +1,29 @@
+/*
+ * Copyright 2017-present Open Networking Foundation
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.onosproject.net.pi.service;
+
+import com.google.common.annotations.Beta;
+import org.onosproject.net.group.Group;
+import org.onosproject.net.pi.runtime.PiActionGroup;
+
+/**
+ * A translator of groups to PI action groups.
+ */
+@Beta
+public interface PiGroupTranslator
+        extends PiTranslator<Group, PiActionGroup> {
+}