Disabled nether portals in galactifun worlds

[IvanMishin1]

Changes

• Disabled creating and using nether portals in galactifun worlds
• Added an option to enable creating and using nether portals in galactifun worlds (false by default)

Checklist

• I have fully tested the proposed changes and promise that they will not break world generation, mob spawning, and the like.
• I followed the existing code standards and didn't mess up the formatting.
• I did my best to add documentation to any public classes or methods I added.
• I have added Nonnull and Nullable annotations to my methods to indicate their behaviour for null values

[Seggan]

Thank you for your contribution