Updates the Field Item Editor to render layers based on the entire map, and the per-patch positioning of each layer.
Import/export will gracefully handle upgrade/downgrade, and viewport import/export will gracefully update tiles rather than a per-acre basis.
Performance has also been slightly improved; no allocation is done anymore when updating the image.
980KB -> 12KB when compressed, seems legit
just an array of tile definitions (32x32 style), sequential acres (undefined acres are all zeroed)
tiles aren't displated as granular as possible, only sets as 16x16 tiles instead of larger 32x32, but it should be a good enough color hint to people for editing
big thanks to ninji for the color mapping in his disassembly and the pbc->tile parse
