Include System-/ENV-Properties into configuration model

[tingrida]

Currently, there are several properties that can only be set as system or ENV variables. These should be added to the configuration model so that they can also be set via the config server.

We may be able to use a dependency or a framework here to facilitate the runtime updates of these properties. Properties such as the polling interval should be changeable at runtime.

Config Priority:

1. Java System Properties
2. OS Environment Variables
3. Property files (.properties)
4. YAML files (.yaml, .yml)
5. Config Server

Acceptance criteria:

• You can configure the HTTP-polling-interval via configuration server