MapGen: Collect all gen into `World/Generetion/...`

[alek13]

• [ ] move to folder
  • [x] lottmapgen
  • [x] icicles
  • [ ] mods/lord/_overwrites/MTG/default/mapgen.lua
    • [x] ores
    • [ ] initialization
    • [ ] papyrus, nyan-cats, ... ???
  • [x] mods/lord/lottores/init.lua:116 (-- Ores Spawning)
• [x] inspect all minetest.register_decoration(), ...
  • created: #1105
• [ ] add cleanup all registered decorations etc. before minetest.register_on_generated()
• [x] add needed decors into lottmapgen/config.lua