Add Update Configuration API

The Device Management Interface needs a gRPC to update device configuration data. A complete startup configuration is an example for that kind of data.

The gRPC shall be designed like the DownloadImage gRPC. Thus the corresponding Protobuf message could contain a field "device_uuid" and a field "configuration_info" which re-uses or is based on the Protobuf message "ImageInformation". The device data to be configured is expected to be hosted by an external server and available via HTTP.

The update of the device configuration shall be a one-step process. There is only one gRPC needed, not two like for updating software (DownloadImage followed by ActivateImage).