DMI - Create rpc to retrieve version/information about the StartupConfiguration of a device

The agreement in the DMI brigade meeting was as below:

• Option to retrieve the cfg.
• Retrieve the configuration version (unique identifier) and the URL (optional) but not the whole configuration
• Document that If the url is not present it means the config is burnt in by the factory.
• Enhance in the future with the full config if we see that we can’t hold NB systems as the only source of truth and that semver of the config is not enough.