Function - HSL color

function to output color from a HSL (hue, saturation, lightness) palette.

リリースノート:

forgot reference, +minor stuff

リリースノート:

fixed a error in the rgb_to_hsl conversion algo, Thanks to @Lord_Voldemort for spotting it.

リリースノート:

fix to hsl function..

リリースノート:

rgb_to_hsl: a few colors still produced saturation, lightness above 100, this should be the final fix for it x_x ..