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/NamespaceListener.java b/utils/yangutils/src/main/java/org/onosproject/yangutils/parser/impl/listeners/NamespaceListener.java
index db53363..4030ada 100644
--- a/utils/yangutils/src/main/java/org/onosproject/yangutils/parser/impl/listeners/NamespaceListener.java
+++ b/utils/yangutils/src/main/java/org/onosproject/yangutils/parser/impl/listeners/NamespaceListener.java
@@ -77,9 +77,9 @@
                                              GeneratedYangParser.NamespaceStatementContext ctx) {
 
         // Check for stack to be non empty.
-        checkStackIsNotEmpty(listener, MISSING_HOLDER, NAMESPACE_DATA, String.valueOf(ctx.string().getText()), ENTRY);
+        checkStackIsNotEmpty(listener, MISSING_HOLDER, NAMESPACE_DATA, ctx.string().getText(), ENTRY);
 
-        if (!validateUriValue(String.valueOf(ctx.string().getText()))) {
+        if (!validateUriValue(ctx.string().getText())) {
             ParserException parserException = new ParserException("Invalid namespace URI");
             parserException.setLine(ctx.string().STRING(0).getSymbol().getLine());
             parserException.setCharPosition(ctx.string().STRING(0).getSymbol().getCharPositionInLine());
@@ -92,13 +92,13 @@
         case MODULE_DATA: {
             YangModule module = (YangModule) tmpNode;
             YangNameSpace uri = new YangNameSpace();
-            uri.setUri(String.valueOf(ctx.string().getText()));
+            uri.setUri(ctx.string().getText());
             module.setNameSpace(uri);
             break;
         }
         default:
             throw new ParserException(constructListenerErrorMessage(INVALID_HOLDER, NAMESPACE_DATA,
-                                                                    String.valueOf(ctx.string().getText()), ENTRY));
+                                                                    ctx.string().getText(), ENTRY));
         }
     }