"Light" already has multiple contexts, but some were missing:
- In general, "Light" refers to a Blender Light object. In many cases,
this comes from an `id_type` enum, already using the ID context. Use
it also for properties that were missing that context.
- In the context of render passes, "Light" is the actual illumination
factor, not the light emitor. A new "Render Layer" translation
context is introduced for this purpose as no existing ones are both
specific and explicit enough.
Issue reported by Hoang Duy Tran.
466af92f7a