YANG Derived Data Type Support + Change in YANG Parser Grammar to 
Support String values which are not in double quotes with UT case + 
Addition of Revision Date Validation with UT case + Removal of 
String.valueOf

Change-Id: Ic152265a35c0d2b0f84473a94ca67681cf8efca8
diff --git a/utils/yangutils/src/main/java/org/onosproject/yangutils/parser/impl/listeners/VersionListener.java b/utils/yangutils/src/main/java/org/onosproject/yangutils/parser/impl/listeners/VersionListener.java
index f9d904d..021ae0d 100644
--- a/utils/yangutils/src/main/java/org/onosproject/yangutils/parser/impl/listeners/VersionListener.java
+++ b/utils/yangutils/src/main/java/org/onosproject/yangutils/parser/impl/listeners/VersionListener.java
@@ -85,7 +85,7 @@
                                            GeneratedYangParser.YangVersionStatementContext ctx) {
 
         // Check for stack to be non empty.
-        checkStackIsNotEmpty(listener, MISSING_HOLDER, VERSION_DATA, String.valueOf(ctx.INTEGER().getText()), ENTRY);
+        checkStackIsNotEmpty(listener, MISSING_HOLDER, VERSION_DATA, ctx.INTEGER().getText(), ENTRY);
 
         Integer version = Integer.valueOf(ctx.INTEGER().getText());
         if (!isVersionValid(version)) {
@@ -110,7 +110,7 @@
         }
         default:
             throw new ParserException(constructListenerErrorMessage(INVALID_HOLDER, VERSION_DATA,
-                                                                    String.valueOf(ctx.INTEGER().getText()), ENTRY));
+                                                                    ctx.INTEGER().getText(), ENTRY));
         }
     }