Django-onfido

This release removes the `is_clear` field from the `BaseStatusModel`, which `Check` and `Report` inherit.

It is replaced by a computed property which checks the `result` for the `Result.CLEAR` and returns as a `bool`.

This is a data change, it now returns `True/False` whereas before it returned `True/False/None`.

When a result is unclear ('consider', 'unidentified') there is a new attribute on the model called `is_clear` which enables admins to mark the record as clear.

The `Event` has been refactored to bring it in line with the other models. This includes a change in field names, hence the minor version bump.

In addition there is improved logging, new batch `fetch` and `pull` queryset methods and a `ONFIDO_TEST_MODE` setting which can be used to bypass signature verification.

Callback view function now supports (in fact enforces) X-Signature verification, as per the [webhook docs](https://documentation.onfido.com/#webhooks).