Airflow-provider-toloka

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* Add `success_on_reasons` param to `WaitAppBatchSensor` init
* Format all docs according to sphinx standard

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* Add `WaitAppBatchSensor` for waiting app batches
* Add `test_connection` method to `TolokaHook` for testing connection from UI
* Add `extra__toloka__url` field for setting `TolokaClient`'s url

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* Update Dockerfile in example.
Now it installs the latest version of Airflow.
* Changed TolokaHook fields:
* Change field for token: now `extra__toloka__token` instead of `password`
* Add separate text field `extra__toloka__environment` for environment
* Hide unnecessary fields in UI
* `toloka_provider.sensors.wait_pool` is `toloka_provider.sensors.WaitPoolSensor` now and is inherited from `BaseSensor`.
Also, name of argument `pool` changed to keyword argument `toloka_pool`.

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* Fixed import troubles

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* Rename package to `airflow-provider-toloka`
* Structure package by standard
* Rename `operators` to `tasks`
* Remove `get_assignments_df`

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* Fixed `open_pool` issues
* Added tests with code coverage