* Unused variables
* Unused values (assigned to variables, but overwritten before use)
* Defining already defined variables instead of reassigning to them.

- Placing liquid inside a protected area no longer returns an empty bucket
- Remove on_place function, tidy up code, return proper itemstack
- Shorten code (changes from HybridDog/patch-35)

Add groups to registration and use water_bucket group

This reverts commit 79856c91.

-> Empty bucket