Sepiida

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The big change here is that I removed the configuration file support. I'm moving everything to use environment variables.
There's various reasons for this but it essentially boils down to the fact that Docker Swarm makes it *much* easier to deploy
updates to environment variables and the 12-factor app (https://12factor.net) recommends it and has solid reasons.

That said, here are the things you'll need to do to upgrade:

1 - Deploy your apps with the new standard set of environent variables:

* API_TOKEN: The internal API token for intra-service communication
* SECRET_KEY: The secret key used by flask for encryption of cookies
* SEPIIDA_JWT_KEY: The JWT key used to sign JWTs
* SERVER_NAME: The value passed to flask for the SERVER_NAME parameter
* STORAGE_SERVICE: https://woodhouse.authentise.com
* TRUSTED_DOMAINS: The list of domains that get CORS support and can receive the API_TOKEN
* USER_SERVICE: https://users.authentise.com

2 - Remove your configuration and configuration_spec fixtures. Fix your tests to stop relying on them
3 - Add a settings_spec fixture that returns your apps environment variable specification, if any
4 - Update sepiida.session.register_session_handler to only pass in the app and an optional whitelist. Stop passing in the pao_root or internal_domains parameter which are now handled by the environment variables USER_SERVICE and TRUSTED_DOMAINS respectively

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Remove support for setting up CORS with a string. It just gets annoying when working with environment variables

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Add the VariableList type and add custom parsers to environment variable specifications

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Don't let celery pump thread give up so easily. Keep it running with exponential backoff retry

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Add the celery pump function to the backend. This is useful for keeping a connection open in
a docker swarm in the face of the virtual IP layer timing out the connection if there is no data
flowing over it. You can use this function with

sepiida.backend.start_celery_pump()

It will create a daemonized thread to send the operations. Backend celery workers will automatically
get the function definition for the null-op function

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