Request for Serialization and Extraction abstraction.

[iankuan]

Hi all,
We plan to give a temporary option for attendee list. However, it's accepted to have a coarser implementation. We create another branch,feature/serialization and feature/extraction, for it.

1. (Optional) Serialization(to JSON) and Extraction(to CSV) abstraction
2. translator to JSON format
3. translator to XML format
4. extract output to CSV format

Example:

• Raw: (yen, uid, timestamp0, timestamp1) -->
• JSON: ("Name", yen, "Uid", uid, "attend_timestamp", timestamp0, "leave_timestamp", timestamp1) -->
• CSV: Attendee list

Notice that extensibility and flexibility should be considered first, such as variable-length raw data. Please follow Mail mechanism and separate interfaces and instances.

In order to eliminate duplication of PR, notify me you are working on it first, please.

[iankuan]

Thank @as23041248 for contribution. Basic serializer interface and json format instance are finished.