Update logic for assignment selection/ranking with new schools & ids

[kevinmulier]

Backend

• Update cron dates
• 4 exams + 2 schools = change our current "bizSchoolCourseId // bizSchoolMidTermChapterId // bizSchoolFinalExamChapterId" system

Frontend

• Update "shouldShowRanking" once the dates are known. Check potential dates issue with assignment_start_date