Adding ctagging systematics and script to fetch correction jsons

Adding ctagging weight systematics and script to fetch correction jsons, this lat one has to be run before running the analysis with the systematics, it is configurable with a dictionary inside the script, that contains the source and destination of the jsons for each systematics, it also create a log file that contains a summary of the information about these files and the relative analysis in which they are used. I also moved the function to flatten the jets in a new misc_utils.py file under higgs_dna/utils/