[module/redshift] allow adjusting the color temperature
[module/redshift] allow adjusting the color temperature

add a boolean flag ("adjust") to redshift that allows the user to have
bumblebee-status actually perform the color adjustment (by invoking
redshift in "one-shot" node).

Note that this only updates the color value each time the redshift
module is updated (every 10s, by default), and likely will collide with
any running redshift process.

fixes #908

tobi-wan-kenobi/bumblebee-status,tobi-wan-kenobi/bumblebee-status