Draft: improved pruneNegligible, removed printout and adding the verbose flag to switch on debugging,

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The present version of the PruneNegligible routing makes a lot of printout in default running, it is also difficult to understand. I removed the printout and added a summary for each pruned systematic that can be activated using the "verbose" tag. Moreover the routine was running also on sampleFolders that didn't represent systematics, they are now skipped ab initio. I think more developing is needed, I think for example that the sum of sample tamplates in each Channel is recomputed for each systematic, this looks an useless resource consumption. I may work on this aspect in future.