New cave type: Magma Caverns.

This is a pretty simple cave composing of some new blocks and possibly a new mob. *Magma Stone which is stone that is charred and has tiny streams of lava flowing through it. *Burnt Stone is dark grey and black with soot. *Basalt Cluster is stone with small shards of Basalt in it. It can drop Basalt shard and 4 make a Basalt block. In these caves a new, unique mob can be found: *Basalt Beast is formed from basalt and has lava rocks in it. It spawns when two basalt are placed on top of Magma block with Magma block arms (a block of Magma on each side of the bottom basalt). It has 36 health and does 4.5 hearts of damage with no armor. It drops a good amount of exp and also Magma Mine. *Magma mine is a trap block that burns mobs and can make small explosion when Redstone is used. This explosion makes fires.