Custom Lightmaps for resource packs in Vanilla

This is a simple addition for us resource pack developers. Allowing the option of custom lightmap creation in Vanilla Minecraft would be great, we would no longer need third-party programs such as Optifine or MCPatcher.

Custom lightmaps would let users create different colored lighting and change the light levels visually (Light levels would still be the same as they are now, they'd just appear different.)

Alright, that's all I have. Please add this in Mojang, it would be a cool, and small addition.