Rework directory structure

share/builtin.lua

share/games/mesetint/mods/bucket/depends.txt

share/games/mesetint/mods/bucket/init.lua

share/games/mesetint/mods/bucket/textures/bucket.png

share/games/mesetint/mods/bucket/textures/bucket_lava.png

share/games/mesetint/mods/bucket/textures/bucket_water.png

share/games/mesetint/mods/default/init.lua

share/games/mesetint/mods/default/textures/crack.png

share/games/mesetint/mods/default/textures/default_apple.png

share/games/mesetint/mods/default/textures/default_book.png

...ames/mesetint/mods/default/textures/default_bookshelf.png

share/games/mesetint/mods/default/textures/default_brick.png

...es/mesetint/mods/default/textures/default_cactus_side.png

...mes/mesetint/mods/default/textures/default_cactus_top.png

...es/mesetint/mods/default/textures/default_chest_front.png

...mes/mesetint/mods/default/textures/default_chest_lock.png

...mes/mesetint/mods/default/textures/default_chest_side.png

...ames/mesetint/mods/default/textures/default_chest_top.png

share/games/mesetint/mods/default/textures/default_clay.png

...mes/mesetint/mods/default/textures/default_clay_brick.png