NLeSC/Xenon: This is release 2.4.0 of Xenon.

What problem does Xenon solve? Many applications use remote storage and compute resources. To do so, they need to include code to interact with the scheduling systems and file transfer protocols used on those remote machines. Unfortunately, many different scheduler systems and file transfer protocols exist, often with completely different programming interfaces. This makes it hard for applications to switch to a different system or support multiple remote systems simultaneously. Xenon solves this problem by providing a single programming interface to many different types of remote resources, allowing applications to switch without changing a single line of code. Notable changes compared to v2.3.0: added name to job description and job status (#609) added max memory to job description (#562) added threads per process to job descriptio