Tweaked textures to be more vibrant and similar to original Minecraft

I've tweaked textures to be more contrast and better-looking with fog. Sand texture is now more vibrant and distinguishable from far. Sky color and textures are more realistic and similar to original Minecraft.

![Img](https://f.cloud.github.com/assets/3747130/322022/4075c716-9a20-11e2-8a42-5ba60621707c.png)

(Left - New version, Right - Old version)