Add different gamma settings for day and night

[lyzkov]

It will be very useful to be able to distinct gamma settings according to changing day and night. In night preset with low brightness factor, gamma tuning increase readability while in day preset it is not necessary anymore.

[maandree]

Perhaps you can use gamma to increase readability, but it not really meant for that. I think it is better to make the programs (ideally implemented in the toolkit) adjust the colours. Gamma is only meant for making the colours look correct (i.e. so the monitor's gamma is actually 2,2.) (Naturally redshift nullifies this adjustment quite a bit.)

Edit: Redshift makes the colours look incorrect, but the colours still look correct relative to each other which is the important part of gamma.

[jonls]

I tend to agree with @maandree on this issue. The gamma setting is really just a hack because Redshift uses the gamma ramps so it will overwrite any existing gamma correction.

[maandree]

@lyzkov If you want to have different gamma settings, I have written an alternative where that is possible.

[lyzkov]

Thanks for advice!

[jonls]

Added in a4052e2