Instanced Scenery has no validation for named and paramter lights used

[tngreene]

Certain rules make a named light or param light instanceable or uninstanceable. We currently don't check those.

A light is instance-able, aka "fast" when
- Custom billboards: these lights are never instance-friendly
- Custom spills: these lights are instance friendly when no dataref is used
- Named/param lights: these lights are instance-friendly when 
-- SPILL_SW is not used for any implementations of the named/param light
-- BILLBOARD_SW is not used for any implementations of the named/param light.

[tngreene]

Put another way:

A light is not instance-able when:

• The light is a custom billboard (LIGHT_CUSTOM)
• The light is a custom spill (LIGHT_SPILL_CUSTOM) and it uses a dataref
• The light is a named/param light and has a SPILL_SW or BILLBOARD_SW implementation

As you can see, lights using datarefs are never allowed.