YANG sub module linking + unsupported yang construct + defect fix

Change-Id: I224c8c14ee2111f6844278cb540c48651544f59b
diff --git a/utils/yangutils/src/main/java/org/onosproject/yangutils/datamodel/YangLeaf.java b/utils/yangutils/src/main/java/org/onosproject/yangutils/datamodel/YangLeaf.java
index c9808a2..f59cdcc 100644
--- a/utils/yangutils/src/main/java/org/onosproject/yangutils/datamodel/YangLeaf.java
+++ b/utils/yangutils/src/main/java/org/onosproject/yangutils/datamodel/YangLeaf.java
@@ -101,6 +101,12 @@
     private YangType<?> dataType;
 
     /**
+     * Default value in string, needs to be converted to the target object,
+     * based on the type.
+     */
+    private String defaultValueInString;
+
+    /**
      * Creates a YANG leaf.
      */
     public YangLeaf() {
@@ -239,6 +245,24 @@
     }
 
     /**
+     * Returns the default value.
+     *
+     * @return the default value
+     */
+    public String getDefaultValueInString() {
+        return defaultValueInString;
+    }
+
+    /**
+     * Sets the default value.
+     *
+     * @param defaultValueInString the default value
+     */
+    public void setDefaultValueInString(String defaultValueInString) {
+        this.defaultValueInString = defaultValueInString;
+    }
+
+    /**
      * Returns the data type.
      *
      * @return the data type