Acacia bush: Create a unique form different to normal bush, with more
leaf nodes at top than at base.
Acacia tree: Maximum height increased by 1 node. 2 extra nodes of
height variation.
Jungle tree: Add an extra node of height variation. Y-slices moved
downwards to be more balanced between trunk and branches, makes
branches more common.
Pine tree: Increase maximum height by 1 node. Add an extra node of
height variation.
Update sapling 'on place' protection checks for acacia and pine trees.
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