The initial implementation of the parallel analysis ended up grinding pcigale to a halt. This was due to the numerous array transfers between the main process and subprocesses. To solve this problem, we now share arrays through a module. This has the advantage
that thanks to copy-on-write, we almost never need to actually copy arrays. Now all the subprocessing run at full speed. Quite a few changes for a patch that only starting with the activation of cache clearing.