Add option to run all steps up to a certain step and selectively save output

[clelange]

Originally posted by @clelange in #89 (comment)_

What about adding options to keep (i.e. copy) the intermediate steps as well? We could also address this in a separate PR later.

My current use case is actually to only run up to the RECO step, and I'd like to keep both GSD and RECO (the only reason for GSD being that we do not have a re-RECO step at the moment), so the ALL step doesn't address my use case, and I was wondering whether one could introduce a "allInOne" option instead of the ALL data tier, and allow for the data tier a comma-separated list that would determine the output to be stored. For example, --datTier NTUP --allInOne would run up to NTUP and only store NTUP, while --datTier GSD,RECO --allInOne would run up to RECO and also keep GSD.