Tree spawning frequency in plains

[Deshiba]

Currently the plains spawn trees with a frequency fitting for a forest rather then a plains. http://i67.tinypic.com/288cjl4.png

Possible solutions:

• Configurable frequency for Fauna spawns to occur (possibly per crystal).
• Splitting the tree generation function to a Forest Crystal.

[baileyholl]

Lowered to 1% chance per block, similar to the savanna crystal now. Dramatically improved. Enjoy!