Ora2

This release focuses on dumping the student's answer in ORA data collection to ensure special/Unicode characters are rendered perfectly in the CSV.

bump edx-submissions requirement version

Generally improves file management from a learner's perspective:
* Existing files are no longer deleted before uploading a new batch of files.
* Allow for the deletion of individual files.
* Allow for much larger (<= 500MB) files to be uploaded.

Related PRs:
* https://github.com/edx/edx-ora2/pull/1290
* https://github.com/edx/edx-ora2/pull/1289
* https://github.com/edx/edx-ora2/pull/1286
* https://github.com/edx/edx-ora2/pull/1282
* https://github.com/edx/edx-ora2/pull/1279
* https://github.com/edx/edx-ora2/pull/1294

Allow for `teams_enabled` key when updating editing context.

Minor changes to migration files to make them compatible with python 3