* Adds emissive carpet, adds plane support to decal element
- Adds a basic abstract/debugging emissive carpet
- Makes decals capable of supporting plane
- Adds auto-smoothing decals
* Adds simple neon carpet variations
* Adds neon carpet reagents and recipes
* Refactors emissive blockers to allow multiple layers of emissive / emissive blocking objects
- Splits the emissive and emissive blocker plane masters into several plane masters which handle different layers of emissiveness.
* Makes neon carpet tile stacks emissive
* Rearranges and docs some emissive plane masters
- Folds the overlay lighting plane master into the emissive planes since it is also used to mask the lighting plane
* Fixes null mats_per_unit stack recombining after splitting
- I think I broke this a while ago when I reworked how stacks handle materials. Whoops.
- This basically only effects carpet at the moment. Good thing I did this when I did!
* Adds neon carpets to cargo
- Adds a cargo supply crate containing a _lot_ of neon carpets for 3000 credits
* Fixes neon carpet highlights leaking through vending machines and such
- Turns out vending machines axed their own emissive blockers whenever they updated their icon because they cleared their managed_vis_overlays...
- Generic emissive blocking has been elementized and some update_overlays procs have been straightened out.
* Fixes id_arg_index for the emissive blocker element
* Commits @Rohsie's suggestions
