Wrong unit for exporting lights

[martty]

Describe the bug
KHR_lights_punctual prescribes the unit of "intensity" for lights, and for point lights this is candela. I have not tested with other lights, but for point lights the exported value is power, which is a different quantity.

To Reproduce

1. Create point light with intensity = 200W
2. Export file into gltf
3. See intensity exported as 200, instead of 200 / (4*pi) or something more correct value

Expected behavior
The power value should be mapped to lumens and then to candela.

Version

• OS: Windows
• Blender Version 2.82

[martty]

Just saw this is a duplicate of #564