add dv::value support to binary_json

src/data/dv.hpp

@@ -220,7 +220,7 @@ namespace dv {
             return setBytes(ptr);
         }
         value& operator=(const objects::Bytes& bytes);
-        
+
         inline value& operator=(const value& v) {
             switch (v.type) {
                 case value_type::object:
@@ -308,6 +308,8 @@ namespace dv {
         }
     };
 
+    inline value none = value();
+
     using reference = value&;
     using const_reference = const value&;
 }