Water, lava and every Forge fluid block can now be placed by survival autoplace, paid for with fluid instead of with an item.
* Fluid costs are registered per block state, water and lava are registered by default, and a registration can ask for fluid even when the block also has an item form.
* A fluid is only placed once the rest of the structure is in place, so it cannot flow out of a half built multiblock, and only the fluid missing from a position is charged, so topping up a leak costs the difference instead of a whole bucket.
* The fluid comes from the player: their fluid containers, plus whatever mods contribute through the new fluid container extractor and fluid source provider registries.
* Existing structure definitions need no change, as ofBlock and the other block elements become fluid elements when the block has no item form.
