Browser kiosk should disable printing

[geofft]

I saw some jobs yesterday in the Pharos queue from kiosk@mit. I saw some more today. The print dialog in the kiosk browser should really be removed entirely, or be replaced with something like "Sorry, buddy, you can only print if you have an MIT account. If you need a campus map or something, go find the admissions office."

[jdreed]

This is harder than it seems, because Firefox is stupid. The r-kiosk home page says:

You might want to remove the print dialog by adding following lines to your user.js:
user_pref("print.always_print_silent",true);
user_pref("print.show_print_progress",false);

However, that doesn't disable printing, just not show the print dialog. Now, we could do something really stupid like remove the "mitprint" printer, or disable CUPS entirely, but this is Hard(tm). The easy solution is to popup a zenity dialog that says "You cannot print. All print jobs will be discarded." or some such.

[jdreed]

r25374 hides the print dialog and also tells the user that it won't work. Doing anything more awesome requires pharos "Popup" for linux or #1033.