Grind enchantments

• The mod's configuration file was split into server- and client-specific parts.
  • Previously, the configuration file was at .minecraft/config/grindenchantments.json. The new files are .minecraft/config/grindenchantments/server.json and .minecraft/grindenchantments/client.json.
  • When starting the game with the new version for the first time, your old config file will automatically be converted to the new format.
• When joining a server, the server-side configuration (like level costs, filters, etc.) is now automatically synced to the client.
  • This means that the client can now always accurately display the level cost on servers.
  • This also fixes an issue where the config was only loaded on the client when loading a singleplayer world – if you didn't, the mod used the default config instead (#70)

Please open an issue on GitHub if you encounter any problems with this!