There should be a config allowing one to enable/disable certain immersions.

It will exist both server-side and client-side, with both configs having to be enabled to allow an immersion to take place. This way, a server admin can disable certain immersions, and a player can also disable immersions if they don't want to use them

Dependency for #24

Things to do:

• Implement the config using Forge's standard config system
• Send a packet from server to client on client join containing all of the server settings
• Combine this with the client's config to get a runtime config
• Add code that makes the runtime config actually do things (with sane defaults while we wait to receive values)

Infrastructure added in 603c97c