Mod support changes:

 * Bewitchment: support new versions, add coquina (Azmalent)
 * Earthworks: new mod! add slate (Azmalent)
 * Natural Pledge: new mod! add certain planks (Azmalent)
 * Railcraft: new mod! add decorative blocks (Azmalent)
 * Roots: add wildwood (Azmalent)

Other changes:

 * Made JSON loading parallel to speed up game loading
 * Minor texture processing optimizations
 * Fixed file I/O leaks
