New decal features: light brightness, resizing, high res

[dmurfet]

Absent a full image uploading pipeline there are still some basic improvements to decals that can be made. The major problems:

• resolution (doesn't Roblox support larger PNGs now?)
• resizing modes
• lighting adjustment

Regarding the final point. We put a light into the boards because otherwise it's generally hard to see writing on the board, but this doesn't work well with decals with white backgrounds (they are washed out). One option would be to automatically disable or reduce by 50% lighting on boards with decals. Alternatively the Decal item that allows you to paste an asset ID can also have a control to set the light level (and possibly also resizing mode).