Change single parts of color

[MariusRumpf]

The library makes use of the color method which requires hue, saturation, brightness and kelvin values. It might be useful to have a method for every single part if it, without affecting others.

For example setting different shades of white is easy with the app but complex with the library. To utilize one has to keep track of the latest color value and only change the kelvin value.

[ristomatti]

This could be done with storing the HSBK values on each change or are they already stored somewhere? I'm using that approach for ristomatti/lifxsh.

In addition a configurable stateColor and stateMultiZone polling interval could be added to notice changes done using other methods.

[MariusRumpf]

That is exactly what I though of, there is no stored value anywhere for now