Added invtweak, tweaked some returns to avoid strange behavior

- Updated news.txt
 - Added invtweak mod instead of old intweak
 - Updated world.mt
 - Tweaked builtin_falling and creative/init.lua to avoir strange behavior from
   the builtin when parsing on_placenode callbacks in creative mode

minetestforfun_game/mods/creative/init.lua

@@ -152,7 +152,7 @@ if minetest.setting_getbool("creative_mode") then
 	})
 	
 	minetest.register_on_placenode(function(pos, newnode, placer, oldnode, itemstack)
-		return true
+		return
 	end)
 	
 	function minetest.handle_node_drops(pos, drops, digger)