Merging diff_pt branch to master.

.gitignore

scripts/postprocessing/README.md

scripts/postprocessing/config_jsons/write_cat_json.py

scripts/postprocessing/convert_parquet_to_root.py

scripts/postprocessing/merge_parquet.py

scripts/postprocessing/prepare_output_file.py

scripts/postprocessing/sample_gen_binning.json