some "ground only" buildings get replaced by a "heavy" tag

it would be nice to have 2 types of 'ground only' buildings, as i see no real reason the folktails log pile cannot be built on platforms, but things like the mine and underground warehouse really do need to be built on land

a 'heavy' building could be built on platforms(maybe just metal ones), but not on top of other buildings due to weight, and not destroying the faction difference between iron teeth and folktales. platforms on top of buildings might not work

a true ground only would have to be placed on a dirt tile