Clarify material and light parameters

[joaander]

Description

Some of the material and light parameters would be more clear with appropriate names.

• Light.color should be intensity
• Material.color should be albedo
• Material.solid should be emit and an RGB. emit=(0,0,0) will be equivalent to solid=0 and a non-zero emit will be equivalent to solid=1, color=emit.

[github-actions]

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