Parralell processing

[ReneSkukies]

Implement parallel processing of multiple subjects.

Maybe with a check if things were already run?

Look at Pipelines.jl and JobScheduler.jl

[behinger]

as discussed, I would put this on low priority for now, given that we have parallelization already in the solver in Unfold.

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Anyway, there are two main ways:

1. Threading (shared memory) with @threads for sub = 1:nsub or so
2. Distributed, where you spawn new julia processes that run a certain program.