Add support for manipulating a color as HSV #597

I have some code that allows me to modify a ColorInt as an HSV color and returns a ColorInt.

Basically I can do something like this:

textView.textColor = Color.RED.hsv { h += 50; s *= 0.5; v = 0.25 }

I think it fits KTX because it leverages Kotlin to abstract some boring stuff about working with HSV (conversion to and from the FloatArray), and uses existing framework Util methods to do the work.

It's a small thing, I have it in this gist.

What do you think?