Fix some undeclared global variables

Addresses #344 and fixes warnings in bucket, default and farming.
```
21:30:26: ERROR[ServerThread]: Assignment to undeclared global "node" inside a function at ...t-servers/bin/../worlds/server/game/mods/bucket/init.lua:138.
21:30:26: ERROR[ServerThread]: Assignment to undeclared global "liquiddef" inside a function at ...t-servers/bin/../worlds/server/game/mods/bucket/init.lua:139.
13:14:16: ERROR[ServerThread]: Assignment to undeclared global "itemstacks" inside a function at ...ers/bin/../worlds/server/game/mods/default/functions.lua:258.
12:56:24: WARNING: Undeclared global variable "wet_lvl" accessed at ...servers/bin/../worlds/server/game/mods/farming/nodes.lua:117
12:56:24: WARNING: Undeclared global variable "wet_lvl" accessed at ...servers/bin/../worlds/server/game/mods/farming/nodes.lua:124 
```
Also removes an unused line in doors which causes a warning.
And might as well remove a few references to .env rather than creating a seperate commit.