Documentation and cleanup still needed for the letterboxing part. The hive resizing part is already thought out and documented. For now this is just a proof-of-concept.
With this MR the thread-count of a SaC application can be changed at runtime by an external controller, with which we communicate through a Unix domain socket.
An example of such a dynamic controller is provided in: https://github.com/JordyAaldering/mtdynamic.