Support Linux

[cklutz]

Linux needs to be supported. This shouldn't be too hard in general, but supporting the "resource limits" might be tricky.

Some links what we could do here, or how others have dealt with it (not checked for correctness or if they suggest something that is actually applicable or usable here, just a list):

• https://unix.stackexchange.com/questions/44985/limit-memory-usage-for-a-single-linux-process
• http://coldattic.info/post/40/
• https://linuxhint.com/limit_cpu_usage_process_linux/
• https://scoutapm.com/blog/restricting-process-cpu-usage-using-nice-cpulimit-and-cgroups
• https://unix.stackexchange.com/questions/134414/how-to-limit-the-total-resources-memory-of-a-process-and-its-children