Modification to generate pdfs with one slide per page

Hi,
As you requested on the lecture, I looked into the code and made a quick edit to generate pdfs with one slide per page. Also I fixed pdf generation when server listens on non-standard port and allowed pdf generating on all html files.

P.S. It would be better to make this functionality optional but I couldn't figure out how to do that with current system of extensions/views.

Gregy - gregope2@fit.cvut.cz