Add Color Temperature on lights

Arnold Light has Temperature controls in at least 3ds Max, Maya and Cinema 4D. We should add those to Softimage as well.
I've been going through the code in MtoA and it's very basic and (I think) it doesn't take into account the rendering colorspace defined in color managers.
I would like to implement it properly in SItoA:
- Temperature slider in Kelvin
- ±Green slider, mimics green/magenta gels on real lights. This is necessary to have on a light for proper color matching.
- Drop-down list with industry standard presets.
- Implementation should query `AiColorManagerGetChromaticities()` to properly convert the XYZ color to the correct rendering color.

I hope in the future that Arnold Cameras also will include a color parameter. This should be implemented with that in mind so that when the day comes the code can just be applied on cameras as well.

Review the existing MtoA implementation and the SItoA light integration first. Confirm how AiColorManagerGetChromaticities() should be used for rendering-color conversion, then define the Kelvin temperature, ±Green, and preset controls; done means Softimage lights expose all three and convert colors correctly for the configured color manager.

Written by the indexing model from the issue text.