Texture alignment

Though you might not see much difference, the changes that I made are important during gameplay. All the stone type boundaries were off by a half cube along all three axes.

I had to modify the terrain shader program extensively, and unfortunately doubled the amount of texture memory required. This means that, to run on computers with 64MB texture memory, the application would need to use lower resolution textures. This is not a problem though, since I believe such graphics cards would not support my shader program anyway.