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

mods/invtweak/README.txt

@@ -0,0 +1,42 @@
+Minetest mod "Inventory Tweaks"
+===============================
+version: 2.0
+
+License of source code: WTFPL
+-----------------------------
+Written 2013-2015 by BlockMen
+
+This program is free software. It comes without any warranty, to
+the extent permitted by applicable law. You can redistribute it
+and/or modify it under the terms of the Do What The Fuck You Want
+To Public License, Version 2, as published by Sam Hocevar. See
+http://sam.zoy.org/wtfpl/COPYING for more details.
+
+License of sounds:
+------------------
+invtweak_break_tool.ogg by EdgardEdition (CC BY 3.0), http://www.freesound.org/people/EdgardEdition
+
+
+~About~
+-------
+This mod add different new functions to Minetest.
+
+First: This mod adds 3 different buttons to player inventory. With those buttons you can sort your inventory easily.
+"<22><>"-Button concernates all stacks to their maximum size.
+"^"-Button sorts all items in an ascending order
+"v"-Button sorts all items in an descending order
+
+NOTE: It's currently only working for the player inventory, not for chests or other formspecs.
+
+Furthermore this mod has the ability to refill your wielded items automaticly. For example your current tool
+break and you have one more of the same type (e.g. a stone pickaxe) this mod put it right in you hand
+and you can keep digging our placing nodes without opening the inventory.
+You can disable this setting by adding/changing following to your minetest.conf file: "invtweak_autorefill = false"
+
+As a small gimmick it adds also a sound when a tool breaks, just to improve the atmosphere of the gameplay.
+
+
+Supported mods:
+- unified_inventory
+- 3d_armor.
+