Async task to update course metadata

[pdpinch]

The source of truth for course titles and dates is the MITx Course Management database in QuickBase. We should be pulling all data from there. Data available from edX's APIs may not be updated in a timely manner.

Acceptance criteria

• [ ] Use course catalog API, i.e. https://api.edx.org/catalog/v1/catalogs/
  • Docs at http://course-catalog-api-guide.readthedocs.io/en/latest/index.html
  • edX has swagger documents describing the library; perhaps they can be used to generate the client code. See https://github.com/edx/api-manager/
• [x] Request service account from edX
• [ ] API client code should be added to the library at https://github.com/mitodl/edx-api-client
• [ ] Update course title, thumbnails and course runs.
• [ ] course runs include short_description, long_description, start (date), end (date), enrollment_start, enrollment_end
• [ ] seats include price and upgrade_deadline