MythArchive: various minor mythburn.py script improvements

* quote all filenames passed to external commands.

* use the feature available in later version of ProjectX to add the PID of the
  stream to the created files to help in choosing which files to use.

  NOTE this requires ProjectX >= 0.91 to work properly it will fall back to
  guessing which files to use so should still work with older versions.

* rework DVD burning to keep trying to successfully burn a DVD prompting the
  user to insert a blank DVD until success or the user cancels the script.

* plus a few other minor fixes.

Closes #10071.

Signed-off-by: Paul Harrison <pharrison@mythtv.org>