* Add color_util.color_hsv_to_RGB
* Use helper functions for LIFX conversions
The LIFX API uses 16 bits for saturation/brightness while HA uses 8 bits.
Using helper functions makes the conversion a bit nicer and less prone
to off-by-one issues.
The colorsys library uses 0.0-1.0 but we can avoid that by using the HA
color_util converters instead.