document workaround to argparse action=append and default combo
use shutil.move instead of os.rename

as per os.rename docs:
    The operation may fail on some Unix flavors if src and dst are on different filesystems

/tmp is often viewed as a different device on Linux systems because it is mounted in RAM.
add qrcode to dependency documentation
don't output GB pass if we're not encrypting
remove unused code
add ubuntu dependency list for people not using the PPA fixes #14
add scripts and documentation to build a Win32 binary of otrfileconverter