Enhance serialization/deserialization for additional properties of DGP model

[tadelesh]

Current behavior:
We treat all additional properties as raw data When serialization/deserialization, not extra typing/format mapping will do for them. So, user could only use them with raw data. If user use model/datetime/timedelta etc. complicated type for additional properties, the ser could do the serialization correctly but only with default behavior (e.g., datetime to rfc3339 format).
Expected behavior:
Serialization: support format etc.
Deserialization: support deserialize with typing info (model type/datetime format/duration format etc).