is ground content revision

see https://github.com/pandorabox-io/pandorabox.io/issues/836

I kept the flowers as ground content to stay in sync with
MTG default flowers. (though I personally would also
mark those as non ground content, but they are passed to
mapgen as decorations...)

init.lua

@@ -43,6 +43,7 @@ for _, clay in pairs(clay) do
 		description = clay[2] .. " " .. S("Baked Clay"),
 		tiles = {"baked_clay_" .. clay[1] ..".png"},
 		groups = {cracky = 3, bakedclay = 1},
+		is_ground_content = false,
 		sounds = default.node_sound_stone_defaults()
 	})
 
@@ -140,6 +141,7 @@ for _, clay in pairs(clay) do
 			},
 			paramtype2 = "facedir",
 			groups = {cracky = 3, terracotta = 1},
+			is_ground_content = false,
 			sounds = default.node_sound_stone_defaults(),
 			on_place = minetest.rotate_node
 		})