Autofeed v2

[pbailie]

The autofeed script has been refactored and improved.

• More maintainable "upsert" queries now use on conflict (...) do update. Original code was written for Postgresql 9.4 which did not support on conflict clauses.
• Code has been better separated into a few different class files to make it easier to maintain these pieces.
• Upsert processing is compartmentalized for each course. That is, a data anomaly for one course will prevent that course from being upserted (to preserve data integrity), but other courses will be upserted normally provided they do not have data anomalies, as well.

Student enrollments report script

• This is run once before the autofeed and once after.
• The first run reads the database and caches enrollment values to a temp file.
• The second run reads the temp file and compares the values with the database. A report is created showing student enrollment adds and drops.
• The report shows the number of students who add or drops from courses registered in Submitty. Only numbers. No names.
• The report may be optionally emailed.