Allow exporting \ printing to match continuous view (one big page)

Please allow exporting in continuous view to look like continuous view, not page view.

I.e. save as PDF or PNG should be able save to one big page that fits the whole score.

This is very useful for putting your score on a tablet or computer screen and reading it by scrolling to a specific place, as well as uploading your score as an image on a website so people can read it while listening to your track without having to click and load a dozen different images.