Add support to print sheet of log representing card backs for duplex printing

Adds the ability to pass a -g or --background flag to the script to print a page of cards with just the logo centered every other page.  This is useful for submitting print jobs to printers that give customers/users the option for duplexing their print jobs, as the logo cards will become the backs of the generated cards from the script.  The flag defaults to false and prints cards without the logo card pages.