switch to a custom arg parser

flag/pflag weren't flexible enough for some of the situations I
want to support or the format I want, so I implemented a simple parser instead
First pass at working SSH connections.

SSH connections are working, including ssh-agent support. A lot
of the glue is in place to make it all async is multiple actions
can run at once too. It's just a matter of filling in the blanks
and testing now ......