Christmas updates

Sorry, quite a big PR... it addresses #1 (closed) and #2 (partially, these probably need more features and improvements) and #3 (closed) and #6 (closed) .

I think that these are most of the dataset-independent things that are needed, the next step would be to find a clean process that we have corresponding data and MC NanoAOD samples for, make some plots and see what is still missing to scale to a full analysis.

Please have a look, I would like to merge it in the next few days (there will be many bugs to fix and things to polish/test/document, but at this stage of development that is not unexpected).