Static foliage colorization

[deathcap]

MC texture packs usually use a grayish color as a placeholder for colormapped grass, leaves, and other living things, see: https://github.com/deathcap/voxel-texture-shader/issues/9

Having colorization support in artpacks may be useful, too. Statically replace the colors on load, as appropriate, so applications using this module can easily reasonably-correctly show these kinds of textures without any extra effort on their part (e.g. for dynamic biome-dependent postprocessing).

[deathcap]

Example of texture needing color: https://github.com/smenes/Faithful32/blob/faithful32_1.6.4/assets/minecraft/textures/blocks/grass_top.png - looks like all shades of gray (R=G=B) are recolored, with an appropriate brightness

[deathcap]

https://github.com/deathcap/graycolorize

[deathcap]

Example using https://github.com/smenes/Faithful32, before:

after (with above commit):