Refactored nature classic global functions
copy&paste error
spawn_plants -> biome.spawn_plants

(only affects legacy string-named function based spawners)
local-ize walldir in vines mod
initialize bush_branch_type to 2
(it needs to be *something* at least)
local-ize a couple more variables
use proper mesh model instead of embedding a node def into
water reedmace entity texture (the latter was used to get plantlike look,
now using a mesh model for same).
fix "floating" plants
caused by a change in how the engine interprets the visual_scale
node def field.
fix tree fern and giant tree fern crowns being too small
remove debug statements
make farming dep optional