if on-gen, saplings grow per their biome_defs.lua settings
if placed, they grow on the surfaces given in the tables:
* anything but palms will grow on the dirt surfaces
* conifers can also grow on a cold surface, but other trees will not
* only palms can grow on sand, but they will not grow on dirt or cold
time. Such saplings will grow very quickly into a tree, compared to a
planted sapling. Defaults to spawning saplings.
add custom jungle tree sapling, alias default one to that, so that
moretrees will be able to grow its own jungle trees.
fix tree density bug
rather than just any trunk being enough to stop just any leaves from decaying.
Re-tuned the leaf decay interval/chance values accordingly. Changed a few
variables to avoid possible conflicts. Added a setting to allow one to disable
the new leaf decay code. Moved sapling growth code into its own file. Minor
changes to comments here and there. Got rid of simple trees list (made the
code do various checks in realtime instead, since it's just startup code
anyway). Fixed messed-up crafting for jungle trees; condensed most of the
crafting code into main craft registry loop. Mostly fixed broken aliases of
default jungletrees.
