[ONOS-3905, ONOS-3901, ONOS-3900] choice, grouping and augment data model support.

Change-Id: Iaee5175e4e06249f5b56192f4744e9297289194c
diff --git a/utils/yangutils/src/main/java/org/onosproject/yangutils/datamodel/YangEnum.java b/utils/yangutils/src/main/java/org/onosproject/yangutils/datamodel/YangEnum.java
new file mode 100644
index 0000000..be3f845
--- /dev/null
+++ b/utils/yangutils/src/main/java/org/onosproject/yangutils/datamodel/YangEnum.java
@@ -0,0 +1,201 @@
+/*
+ * 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.datamodel;
+
+import org.onosproject.yangutils.datamodel.exceptions.DataModelException;
+import org.onosproject.yangutils.parser.Parsable;
+import org.onosproject.yangutils.parser.ParsableDataType;
+
+/*-
+ * The "ENUM" statement, which is a sub-statement to the "type"
+ *  statement, MUST be present if the type is "enumeration".  It is
+ *  repeatedly used to specify each assigned name of an enumeration type.
+ *  It takes as an argument a string which is the assigned name.  The
+ *  string MUST NOT be empty and MUST NOT have any leading or trailing
+ *  whitespace characters.  The use of Unicode control codes SHOULD be
+ *  avoided.
+ *
+ *  The statement is optionally followed by a block of sub-statements that
+ *  holds detailed ENUM information.
+ *  All assigned names in an enumeration MUST be unique.
+ *
+ *  The ENUM's sub-statements
+ *
+ *                +--------------+---------+-------------+------------------+
+ *                | substatement | section | cardinality |data model mapping|
+ *                +--------------+---------+-------------+------------------+
+ *                | description  | 7.19.3  | 0..1        | - string         |
+ *                | reference    | 7.19.4  | 0..1        | - string         |
+ *                | status       | 7.19.2  | 0..1        | - YangStatus     |
+ *                | value        | 9.6.4.2 | 0..1        | - int            |
+ *                +--------------+---------+-------------+------------------+
+ */
+
+/**
+ * Maintains the ENUM data type information.
+ */
+public class YangEnum implements YangCommonInfo, Parsable {
+
+    /**
+     * Named value for the ENUM.
+     */
+    private String namedValue;
+
+    /**
+     * Description of the ENUM value.
+     */
+    private String description;
+
+    /**
+     * Reference info of the ENUM value.
+     */
+    private String reference;
+
+    /**
+     * Status of the ENUM value.
+     */
+    private YangStatusType status;
+
+    /**
+     * value of ENUM.
+     */
+    private int value;
+
+    /**
+     * Create a YANG ENUM.
+     */
+    public YangEnum() {
+
+    }
+
+    /**
+     * Get the named value.
+     *
+     * @return the named value.
+     */
+    public String getNamedValue() {
+        return namedValue;
+    }
+
+    /**
+     * Set the named value.
+     *
+     * @param namedValue the named value to set.
+     */
+    public void setNamedValue(String namedValue) {
+        this.namedValue = namedValue;
+    }
+
+    /**
+     * Get the description.
+     *
+     * @return the description.
+     */
+    public String getDescription() {
+        return description;
+    }
+
+    /**
+     * Set the description.
+     *
+     * @param description set the description.
+     */
+    public void setDescription(String description) {
+        this.description = description;
+    }
+
+    /**
+     * Get the textual reference.
+     *
+     * @return the reference.
+     */
+    public String getReference() {
+        return reference;
+    }
+
+    /**
+     * Set the textual reference.
+     *
+     * @param reference the reference to set.
+     */
+    public void setReference(String reference) {
+        this.reference = reference;
+    }
+
+    /**
+     * Get the status.
+     *
+     * @return the status.
+     */
+    public YangStatusType getStatus() {
+        return status;
+    }
+
+    /**
+     * Set the status.
+     *
+     * @param status the status to set.
+     */
+    public void setStatus(YangStatusType status) {
+        this.status = status;
+    }
+
+    /**
+     * Get the value.
+     *
+     * @return the value.
+     */
+    public int getValue() {
+        return value;
+    }
+
+    /**
+     * Set the value.
+     *
+     * @param value the value to set.
+     */
+    public void setValue(int value) {
+        this.value = value;
+    }
+
+    /**
+     * Returns the type of the data.
+     *
+     * @return ParsedDataType returns ENUM_DATA
+     */
+    public ParsableDataType getParsableDataType() {
+        return ParsableDataType.ENUM_DATA;
+    }
+
+    /**
+     * Validate the data on entering the corresponding parse tree node.
+     *
+     * @throws DataModelException a violation of data model rules.
+     */
+    public void validateDataOnEntry() throws DataModelException {
+        // TODO auto-generated method stub, to be implemented by parser
+    }
+
+    /**
+     * Validate the data on exiting the corresponding parse tree node.
+     *
+     * @throws DataModelException a violation of data model rules.
+     */
+    public void validateDataOnExit() throws DataModelException {
+        // TODO auto-generated method stub, to be implemented by parser
+    }
+}