[Feature] Config Loader API

[justaureus]

• I have checked that I am on the latest version of Terra.
• I have searched github for similar features requests, including closed
  ones, and found none.
• I believe this is within the scope of Terra.
• This feature request is for all of Terra, and isn't something that
  should be implemented by a pack or addon.

Feature Description

API methods to load config packs provided by mods/plugins other than Terra.

What Problem Does This Solve?

This would allow other mods/plugins to provide Terra config packs to offload the world generation to Terra as a dependency.

A Solution You'd Like

This would require additional API methods to support this functionality.

Alternative Solutions

1. Packaging Terra and a config pack as a standalone mod.
   This gets into licensing issues as well as being less friendly to other developers wanting to use Terra in conjunction with their own mods.
2. Adding packs to the Terra packs directory.
   This could introduce load-order issues as well as other problems.