Plank Texture Swap

Swaps appearance of planks and treated planks. This mod is purely cosmetic, only the appearance is changed, not any recipes. I made this because it always seemed backwards to me that the freshly-cut planks were stained brown but the treated planks were the colour of newly-sawn wood. The platforms and stairs made using the planks are dark brown because they're painted, just like the little white handrails :)