Improve logging with Google Cloud Logs

[dividehex]

    The primary purpose here is to improve logging to GCP by
    changing the logging formatter from plaintext to json.  The
    python logging config is now unified under logging.ini for both
    the flask application and gunicorn.

    Other changes are listed here:
    * Limits everret config sources to ENV only to avoid confusion
    * Removes sso-dashboard logger in favor of the root logger
    * Log Levels set to INFO unless SSO-DASHBOARD_DEBUG is set True
    * Adds a flask handler for uncaught Exceptions