Clean up logging and ReleaseStation constructor

- Don't use basicConfig, actually set up logging to STDERR
  for both regular and debug invocations
- Don't print to sys.stderr, use the logger
- Use consistent exit codes
- Do not call _errDialog (and by extension, GtkDialog.run())
  outside the main loop.
- It is a fatal error if something bad happens in the middle of
  reading a card
Reset the login screen upon authentication fail

- If authentication fails, reset the login screen
Hide the "swipe card" graphics if no reader

If there's no card reader, hide the "Swipe your card"
graphics.