new feature: color temperature

This feature is inspired by tools such as "f.lux" or "redshift". You can set color temperatures for day and night operation. For further info have a look at "http://www.stereopsis.com/flux/" or "http://jonls.dk/redshift/".
As I understood "f.lux" and "redshift" use gamma ramps to simulate color temperature changes. In contrast "AMDOverdriveCtrl" sets true color temperatures by using AMD ADL calls. The results should be quite similar.