Refactoring audit subsystem to clean-up and eliminate back-dependency from core to CLI; still needs additional work.

Change-Id: I93c04c94f27b7b89c582b359eebe125458a573a7
diff --git a/core/api/src/main/java/org/onosproject/security/AuditService.java b/core/api/src/main/java/org/onosproject/security/AuditService.java
new file mode 100644
index 0000000..f98eda4
--- /dev/null
+++ b/core/api/src/main/java/org/onosproject/security/AuditService.java
@@ -0,0 +1,39 @@
+/*
+ * Copyright 2018-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.security;
+
+/**
+ * Service for enabling audit logging.
+ */
+public interface AuditService {
+
+    /**
+     * Returns true if auditing is enabled.
+     *
+     * @return true if audit enabled; false otherwise
+     */
+    boolean isAuditing();
+
+    /**
+     * Logs the specified user action.
+     *
+     * @param user   user that initiated the action
+     * @param action action being logged
+     */
+    void logUserAction(String user, String action);
+
+}