[NTG-context] duplex printing

[Pablo Rodriguez]

Dear list,

for those interested, Hans has implemented in latest beta from
2015.12.22 10:50 values for duplex printing in the option key from
\setupinteractionscreen.

With this commit, it is possible to disable duplex printing in printers
which have it set by default, or enable portrait or landscape duplex
printing (no matter which the defaults are).

More information at http://wiki.contextgarden.net/PDF_Print_Options. I
must admit it is formatted like crap. But I had to write it in Markdown
and convert it to mediawiki using pandoc.

I hope you enjoy this feature,

Pablo
-- 
http://www.ousia.tk