Populate args[0] with the process name

ISSUE: ``med help rs`` starts the runserver rather than display help

According to: http://docs.python.org/2/library/os.html#os.execvp
args[0] should be the name of the chipd process.

Making this change displays help correctly for rs.
Improvements to help

help output for help command
subcommander accepts --help for help command (allows subcommander
    instances used as subcommands to show help)
Strip outer ""'s, so DESC="Usage" looks better
Merge pull request #2 from aarcro/amcm_fix_help

Minor improvements to help command