perlin noise based terrain generation, trees, basic biomes

Perlin noise based terrain generation with  trees (birch and oak) and biomes based on height (beach near or at sea level, extreme hills edge  a bit above beach and extreme hills elsewhere) up to ten trees per chunk. stone forms 2/3 of the land with dirt the remaining third. rare gravel generation on the top layer rare clay generation in rivers and sand for beaches and underwater
![2013-09-21_11 57 09](https://f.cloud.github.com/assets/4346030/1185503/b485533c-22ac-11e3-9afe-a6b22995901c.png)