Add option to run OpenMP threaded jobs

[arnikz]

No description provided.

[arnikz]

xenon-cli options:
with SGE: --option parallel.environment=threaded --option parallel.slots=... (using -pe threaded ...)
with SLURM: ??? (should use --cpus-per-task=...)

It would be nice to have single option common to both (all) schedulers so that the xenon command requires a single change only i.e. gridengine or slurm. One could harmonize the options across schedulers using e.g. a config file (incl. user-defined mappings).

[jmaassen]

A bit more info on translating the various options:

https://slurm.schedmd.com/rosetta.pdf

[arnikz]

I've used a similar conversion table for my use case (see here) but it did not work with my OpenMP program so I've followed this suggestion, which worked fine:)