Allow adjusting screen color temperature (like f.lux, redshift)

[v-l]

Haiku lacks the option of changing screen color temperature (​https://en.wikipedia.org/wiki/Color_temperature), that is, making the screen redder in the evenings to reduce eye strain.

On Windows and Linux, this is done with f.lux and Redshift applications: ​https://en.wikipedia.org/wiki/F.lux ​https://en.wikipedia.org/wiki/Redshift_(software)

Implementing this in Haiku (or as a separate program) would make Haiku much more usable for users who work in the evening. I think this could be done by letting users or programs change gamma correction of the screen.