* plug-ins/Lighting/lighting_main.c
	* plug-ins/Lighting/lighting_main.h
	* plug-ins/Lighting/lighting_preview.c
	* plug-ins/Lighting/lighting_preview.h
	* plug-ins/Lighting/lighting_shade.c
	* plug-ins/Lighting/lighting_ui.c: completely reworked UI for
	lighting page.  Now supports up to 6 lights (more is trivial).
	Added ability to temporarily isolate selected light.  Added
	light intensity controls.  Can interactively position each light
	(does not quite work yet for directional lights).