Use default window.print function for special nids

Hi, in some use cases you can't load the special print-friendly page, but the default print.css file.

Specially my problem was the get_directions page. Where the user first generate the directions map with his route, and if I used the callback for print, the map and the route was lost of course.

To stay with print-links, i made a patch.
The patch adds a new settings field to the print config page, where you can add the nids, which schould use the default browser print function.

The logic is very simple: just override the $path variable to '#' and sets the attribute "onclick" to "window.print()".

So, please if somebody is interested in this, download the patch and try it out.
thanks, dropfen