Extracted StringReader and StringWriter from JsonParser

Split `Internals/` folder into `Data/`, `Deserialization/`, `Serialization/`

include/ArduinoJson/Serialization/DummyPrint.hpp

@@ -0,0 +1,21 @@
+// Copyright Benoit Blanchon 2014-2016
+// MIT License
+//
+// Arduino JSON library
+// https://github.com/bblanchon/ArduinoJson
+// If you like this project, please add a star!
+
+#pragma once
+
+#include "../Print.hpp"
+
+namespace ArduinoJson {
+namespace Internals {
+
+// A dummy Print implementation used in JsonPrintable::measureLength()
+class DummyPrint : public Print {
+ public:
+  virtual size_t write(uint8_t) { return 1; }
+};
+}
+}