Create backups of arbitrary data to paper using qrencodes. Data is split
across several pages automatically.

Usage is something like:

    # create a backup
    gpg --export-secret-key | paperkey | paperback | lpr

    # restore; you'll need to present the qr pages in order
    zbarcam --raw | base64 -d | paperkey --pubring ... | gpg --import

Requires:

  - qrencode
  - imagemagick
  - zbar
  - psjoin (from psutils)

TODO:

  - can probably fit more data per page; needs testing

  - could possibly use 8bit QR encoding, but zbar does not seem to
    support it

  - "part" title gets cut off by some printers; probably needs better
    margins

  - title should be customizable