Update config in Dockerfile (#68)

[joemat]

• run cargo clippy and fix all issues

• run cargo fmt to format all source files

• Extracted creation of config.toml to a script on order to make it better readable

• Fixed putting values from environment variables to config.toml

Fixes #56

[DennisOSRM]

Suggested change

	[simple_mqtt]
	host = "$MQTT_BROKER_HOST"
	username = "$MQTT_USERNAME"
	password = "$MQTT_PASSWORD"
	port = $MQTT_PORT

this would also publish the data using the simple MQTT publisher's topics.

[joemat]

sorry, had some issues with my branches, created a new PR #70 that also contains the changes suggest by you @DennisOSRM