Store records related to the past terms

[kyoshizaki]

Issue

• Drop all existing records and insert new records in tables for each import process.
• The records related to the past terms are deleted from DB.

Fixed Import job procedures

• Create new records and update existing records
• Delete class and enrollment records when it was disappeared from CSV file within the stated terms.

Remarks: works for this issue

• Set unique index for sourcedId in each tables
• Use "On Duplicate Key Update" option for bulk update
  • ATTENTION: "On Duplicate Key Update" option has DB dependency (MySQL is default DB).
• Delete class and enrollment records when...