simfactory's setup-silent should set the default number of threads a number smaller than the number of cores found

[Roland Haas]

Currently simfactory's setup-silent sets the default number of threads to the number of (logical) CPUs found. While this is somewhat sensible it means that if one runs a simulation using RotatingSymmetry180 then one has to manually set --num-threads to a non-default value, otherwise the code aborts.

On a workstation or laptop the a simulation usually runs fastest if using only MPI and not OpenMP, ie. num-threads=1 (see the discussion in #2059).

I would like to advocate to change this default to be num-threads=2 for a machine with an even number of cores and num-threads=number-of-logical-cpus (ie the current value) for odd numbers of cores (which really should be only those rare single core machines anymore).