Bake static lighting

Lightmaps remove per-frame shadow and lighting cost for static lights on static geometry.

• Application registers Lightmapper; manual AppOptions bootstraps set lightmapper = Lightmapper.
• On the light, set bake = true; once every mesh it lights is lightmapped, set affectDynamic = false.
• On each mesh, set render.lightmapped = true, or it goes unlit once affectDynamic is off. Size it with lightmapSizeMultiplier; castShadowsLightmap lets meshes shadow each other.
• Set the mode on scene.lightmapMode: BAKE_COLOR for flat diffuse, or the default BAKE_COLORDIR, which adds direction for normal- or specular-mapped materials.
• Bake AO without lights with scene.ambientBake, ambientBakeNumSamples, and ambientBakeOcclusionBrightness and ambientBakeOcclusionContrast.
• The Engine bakes once on the first rendered frame. Call app.lightmapper.bake(null, mode) only for nodes added later or to re-bake.

A second UV set is required