Light groups as a Plasma modifier

Right now light groups are handled using the Blender's existing (per-material) system, but there are times it is better to assign light groups on a per-object basis rather than per-material.

Additionally, the material light group option only allows setting a single group (which admittedly is not much of a problem since lamps can belong to multiple groups).

I'm imagining a Plasma Modifier to set groups on a per-object basis. My current thinking is that the modifier would always take precedence over the material light group:

if bobj.plasma_modifiers.light_groups:
  # Use the light groups from the modifier
elif bobj.material.light_group:
  # Use the material light group
else:
  # Default

The issue does not name files or tests; start by tracing how the existing per-material light-group handling is implemented in the Blender addon. Define the modifier's per-object group behavior and precedence over material groups, then verify that multiple groups and the default case work as described.