With the current argparse docs, it's very hard to get a quick reminder of how to spell the various parameters for add_argument, and just what they do. This issue suggests adding a "Quick Reference" section for add_argument, with the following elements:

1. Summary table with a one line description of each parameter
2. Summary table with a one line description of each alternative for the "action" parameter (including noting which other parameters are potentially relevant, such as 'choices' and 'metavar' for 'store' and 'const' for 'store_const')
3. Summary table with a one line description of each alternative for the "nargs" parameter