Change single voice PDF page to A4 landscape

Added new parameters ```PrintParam.DEFAULT_A4PartLandscape``` so the voices are rendered in the PDF on A4 landscape pages.

Using the ```PrintParam``` is also a better way to solve the problem addressed in pull request #7.
this change makes this menu item exactly the same as the one below it (LL2015-2016), "Print preview". no point having two options do the exact same thing