[DVD-o-matic] letterboxed input formats

Like adding some formats that includes the cropping. Actually, I always use "Flat without stretch", I consider the rest Advanced use. Maybe some direct acces to ffmpeg parameters? instead on growing the formats list to infinity. Already got a couple of Scope inside a 1920x1080, and I expect to get many more like that. And for SD material (old short films) I would expect 16:9 inside 4:3 and even scope inside 4:3 (oh yes, got that in a DV file last week) Thanks! Manuel AC