Feature Update

1. Rearrange the data structure of GPA.json and related .qml
2. Add functions to write record into GPA.json
3. Modify some function prototype in MyListModel to integrate with
RecordModel
4. Add condition judgment before writing new record

Known bugs:
1. need to adjust the order of r/w data from/to GPA.json file
2. need to be more specific on the record time