Minetest 5.1-dev+ mod: Simple helicopter

originally by Pavel_S
reworked by DS

Todo:

• Replace craftitems and recipes
• Add screenshot and description
• Add code license
• Fix that z-fighting

License of source code:

original code by Pavel_S: GPL_v2 (see file LICENSE)
changes / complete rework by DS: License to be chosen
matrix.lua file: CC0

License of media (textures and sounds):

helicopter_motor.ogg by Robinhood76 | License: Attribution Noncommercial

helicopter_water_driblet.png by DS | License: CC0

helicopter model and texture:

Bell47 is a FREE 3D model made by Melkor (https://forum.minetest.net/memberlist.php?mode=viewprofile&u=301) for the free game "Minetest" and is released under CC-BY-NC-SA 3.0 http://creativecommons.org/licenses/by-nc-sa/3.0/
For more information, see Licence.txt
(+ Modified by DS)

the item textures are probably by Pavel_S, TODO