Add Night Light color slider

Commits

display: Add Night Light color slider

This adds a scale to change the color temperature from 3000K to 6000K. A mark is added to the default value and a second one for aesthetics.

Initial implementation by Benjamin Berg

Color choices by Daniel Foré and elementary OS

Closes #147 (closed)

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night-light: Drop the sunrise/sunset indicator

It's not in the latest design mockup:

https://gitlab.gnome.org/Teams/Design/settings-mockups/raw/master/displays/night-light.png

Comments

I'd like to work on other changes from the mockup after this is merged.

elementary uses a range from 3500-6000 with a default of 4500. I used a range of 3000-6000. Our default is 4000.

Screenshots