load_all_csvs_to_model now displays top level progress bar and ETA based on sum of csv file sizes in bytes
fix progressbar counter
preprocess files and sort the list in load_all_csvs_to_model()

TODO: preprocess should catalog the entire list of files (full paths), their sizes, and number of lines and
      sort it lexographically by path to get consistent (more efficient due to proximity?) ordering in DB pk's?