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.
Ah I didn't notice that difference and was wondering why it was there were multiple ways to to access the same option.

I was trying to solve an issue that rendered parts in a PDF like this:
![screen shot 2014-07-05 at 01 26 17](https://cloud.githubusercontent.com/assets/3244729/3485311/d32f37aa-03d2-11e4-9254-fc3ff90d66b9.png)

The proposed changed solved that problem, but it seems I haven't solved it in the correct way. I'll have another look later. Thanks for your reply!