New GUI package

The old 2010 Qt4 dvda-author-package, which was broken, has been fixed for most issues and somewhat simplified.
Some minor bugs remain.
However the GUI will make it easier for some to author hybrid discs (which can play on either DVD-Audio or DVD-Video players).
The hybrid-authoring capability has been made possible thanks to a (forked version of) Lplex, originally created by Bahman Negahban on sourceforge and now unmaintained by the original author.
Other bug fixes will follow on.