only use stream for serialisation

include/sp/common/VarInt.h

@@ -7,7 +7,8 @@
 
 #include <cstddef>
 #include <cstdint>
-#include <sp/protocol/MessagePrinter.h>
+#include <ostream>
+#include <sp/protocol/Field.h>
 
 namespace sp {
 
@@ -56,11 +57,8 @@ class VarInt {
 	 * \param var The variable integer to deserialize
 	 */
 	friend DataBuffer& operator>>(DataBuffer& in, VarInt& var);
+
+	friend std::ostream& operator<<(std::ostream& a_Stream, const PrintableField<VarInt>& a_VarInt);
 };
 
-template<>
-inline std::string PrintData(const VarInt& a_VarInt) {
-	return PrintData(a_VarInt.GetValue());
-}
-
 }  // namespace sp