Upgrade bumblebee and add nixos module

 * Bump bumblebee to 3.2.1
 * Remove config.patch - options it added can be passed to ./configure now
 * Remove the provided xorg.conf
   Provided xorg.conf was causing problems for some users,
   and Bumblebee provides its own default configuration anyway.
 * Make secondary X11 log to /var/log/X.bumblebee.log
 * Add a module for bumblebee