Added CSV processor

[davestgermain]

This adds a reusable CSV file processor that can handle:

• row validation
• file format validation
• checksums based on arbitrary columns
• two-stage commit
• undo of committed data
• asynchronous file processing using celery

Current use cases are for Staff Graded Points, Gradebook import/export, and Program Enrollment import/export.

[nasthagiri]

@davestgermain This is great functionality. Can you put this in a new repo? This is not necessarily a feature that all Django apps will need. Let me know if you want me to create the new repo for you.

[davestgermain]

@nasthagiri I wasn't sure if it needed a new repo. I can do that (though I wish it didn't require an IT ticket every time). For simplicity, would this be a cookiecutter django app repo, even though it isn't a django app?

[davestgermain]

Moved to davestgermain/super-csv