Create app

Create django application providing annotator-storage functionality.

https://openedx.atlassian.net/browse/TNL-780
> The expectation was that this would be reading the settings from a yml configuration file, is that in a separate PR? I would prefer that we read from a yml file in dev mode as well to preserve symmetry and make it very clear how values are set and which one are typically overridden.

This will be in a separate PR. Added story for this: https://openedx.atlassian.net/browse/TNL-902