Upgrade Python->3.5, Gunicorn->19.9.0 (#1423)

add endpoint to export enrollment

add tls k8s config

Move assign_grading_queues to a worker job

fix: remove meaningless ORDER BY clause from export grades

fix: disable extension request feature (#1412)

feat: sort assignments by due date for staff (#1411)

feat: let students make extension requests (#1409)

feat: update web and worker deploys to api apps/v1

feat: use volume mounts for ssl

fix: use the azure template for google cloud sql certs

fix: add server ssl handling to workers as well

fix: python3.5 doesn't support f-strings

feat: support ssl auth for database

Merge pull request #1410 from okpy/batch-enroll-replace-option