Different periods per terms cannot be exported

Courses that have different periods per terms cannot be exported.

Test cases:

- `01EH128`
- `01EJ636`
- ~`EB10053`~
- ~`FCB1311`~
- ~`FCB1321`~
- ~`FCB1331`~
- ~`FCB1301`~

Current output schema cannot express this rule of schedule. Maybe it should be fixed with next major update.