Store API tokens encrypted in the database.
During the database migration a randomly generated key will be used encrypt the tokens if no ENCRYPTION_KEY environment variable was provided.
If the application is started without the presence of an ENCRYPTION_KEY (or if the key failed to decrypt the existing tokens), the UI will display a warning with further instructions.
* Add option HTTP_BINDING_ADDRESS to control the IP address where the web interface is exposed.
* Fix doc typo.
* Keep mix format quiet with some empty lines.