The "required" parameter to argparse.add_subparsers() was only
added in python 3.7. However, given that it defaults to 'required'
and was always unconditionally required even in python 2.x,
we can safely remove it.
Change-Id: Ia0ffca055f47016fb29ef009acecac2a139e4077
Do away with most of the hard-coded defaults and allow user to specify
a variety of parameters via the command line. Also, start to use
argparse subparsers for better usability
Change-Id: Ib7b8121676bef9310f219affc6f3cc76b6986b2a
Harald Welte