Get or sets the additional special properties (cfr $id, $ref, $type, &value and $values) and it handling functions.
ex: A json can contain a special deferred property:
"Patient": {

 "$deferred": "http://server/patients/457892/",

}
so you can create something like oData Deferred Content http://www.odata.org/developers/protocols/json-format#DeferredContent

SpecialPropertiesReadHandling.Add("$deferred", (reader, objectType, contract, member, existingValue, target, reference, serializer) =>
{
reader.Read();
string value = (reader.Value != null) ? reader.Value.ToString() : null;

Debug.WriteLine(value); //in our example will print "http://server/patients/457892/" //here we can do some cool stuff like creating a dynamic proxy that will handle the deferred loading reader.Read();
return null;
});

setting the "$deferred" property can be done by a custom converter