Create app

Create django application providing annotator-storage functionality.

https://openedx.atlassian.net/browse/TNL-780
@olmar Yes, cleaning up other repos is something we'd like to take care of, such as the dashboard repo. At this point, that is tech debt and we'd need to invest the time into clean up. For this PR, I'd rather not start with making exceptions; it'll be easier if we have 100% enforcement to start with.