[ONOS-3882, 3883, 3892]Implement Yang container, list, leaf, leaf-list parsing

Change-Id: I39039c91385fe0d530d037350ef7833c2459514d
diff --git a/src/main/java/org/onosproject/yangutils/parser/impl/listeners/ContainerListener.java b/src/main/java/org/onosproject/yangutils/parser/impl/listeners/ContainerListener.java
new file mode 100644
index 0000000..b77f594
--- /dev/null
+++ b/src/main/java/org/onosproject/yangutils/parser/impl/listeners/ContainerListener.java
@@ -0,0 +1,87 @@
+/*
+ * Copyright 2016 Open Networking Laboratory
+ *
+ * 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.yangutils.parser.impl.listeners;
+
+import org.onosproject.yangutils.parser.antlrgencode.GeneratedYangParser;
+import org.onosproject.yangutils.parser.impl.TreeWalkListener;
+
+/*
+ * Reference: RFC6020 and YANG ANTLR Grammar
+ *
+ * ABNF grammar as per RFC6020
+ *  container-stmt      = container-keyword sep identifier-arg-str optsep
+ *                        (";" /
+ *                         "{" stmtsep
+ *                             ;; these stmts can appear in any order
+ *                             [when-stmt stmtsep]
+ *                             *(if-feature-stmt stmtsep)
+ *                             *(must-stmt stmtsep)
+ *                             [presence-stmt stmtsep]
+ *                             [config-stmt stmtsep]
+ *                             [status-stmt stmtsep]
+ *                             [description-stmt stmtsep]
+ *                             [reference-stmt stmtsep]
+ *                             *((typedef-stmt /
+ *                                grouping-stmt) stmtsep)
+ *                             *(data-def-stmt stmtsep)
+ *                         "}")
+ *
+ * ANTLR grammar rule
+ *  containerStatement : CONTAINER_KEYWORD IDENTIFIER
+ *                   (STMTEND | LEFT_CURLY_BRACE (whenStatement | ifFeatureStatement | mustStatement |
+ *                   presenceStatement | configStatement | statusStatement | descriptionStatement |
+ *                   referenceStatement | typedefStatement | groupingStatement
+ *                    | dataDefStatement)* RIGHT_CURLY_BRACE);
+ */
+
+/**
+ * Implements listener based call back function corresponding to the "container"
+ * rule defined in ANTLR grammar file for corresponding ABNF rule in RFC 6020.
+ */
+public final class ContainerListener {
+
+    /**
+     * Creates a new container listener.
+     */
+    private ContainerListener() {
+    }
+
+    /**
+     * It is called when parser receives an input matching the grammar
+     * rule (container), performs validation and updates the data model
+     * tree.
+     *
+     * @param listener listener's object.
+     * @param ctx context object of the grammar rule.
+     */
+    public static void processContainerEntry(TreeWalkListener listener,
+                                             GeneratedYangParser.ContainerStatementContext ctx) {
+        // TODO method implementation
+    }
+
+    /**
+     * It is called when parser exits from grammar rule (container), it perform
+     * validations and updates the data model tree.
+     *
+     * @param listener listener's object.
+     * @param ctx context object of the grammar rule.
+     */
+    public static void processContainerExit(TreeWalkListener listener,
+                                            GeneratedYangParser.ContainerStatementContext ctx) {
+        //TODO method implementation
+    }
+}