Denser jungletree for darker rainforest:
Highest 'jungletree' nodes now prob 255.
Add a 5th lower branch layer.
Increase lower branch layer y-slice prob to 191.
Aspen:
Extend trunk upwards by 1 node to reduce leafdecay radius to 2.
Pine:
Make lower trunk 1 node longer so that lowest branches are more often
higher off the ground, also to make pines taller.
Appletree:
Make 2 opposite branches prob 255, the other 2 prob 127, to avoid
trees with 1 or 0 branches. Therefore also add random rotation.
