-Added WriteObjectId to BsonWriter
-Added BsonObjectId and BsonObjectIdConverter classes
-Added KeyValuePairConverter
-Added DynamicCodeGeneration flag to DefaultContractResolver
-Changed JsonConverter.ReadJson to add an extra parameter: currentValue
-Added CustomCreationConverter
-Added IsReference to JsonContainerAttribute
-Added PreserveReferencesHandling to JsonSerializer
-Added IReferenceResolver to JsonSerializer
-Split internals of JsonSerializer into JsonSerializerWriter (serializes) and JsonSerializerReader (deserializes)
-Moved serialize stack from JsonWriter (yuck) to JsonSerializerWriter (yay)
-Added FromObject overload with JsonSerializer argument for cases when state is needed