ctffind_plot_results.sh and pdftk

ctffind_plot_results.sh requires pdftk which is no longer well supported and not available on recent releases of Fedora, RHEL or CentOS. Since pdftk is used only for changing the document's title, exiftool would be an alternative. Attached is a patch to add exiftool support as an alternative to pdftk.

Hi -
thanks a lot for the hint. I hadn't realized pdftk wasn't easy to get - I believe it's available in the main repositories for Ubuntu, which is the OS I use.
I appreciate the patch and will modify the script for the next release.