interfaces: add ObjectTrackingInterface

The ObjectTrackingInterface is used by object tracking and provides
basic information about the tracker. The interface is mainly used for
messages. The SuggestIdMessage defines the id which the next object
should be given.
object-tracking: allow to suggest IDs for the next new object

When a SuggestIdMessage (defined in the ObjectTrackingInterface) is sent
to the tracker, the suggested ID will be assigned to the next new
object.