增加配置文件自定义路径功能

patches/net/minecraftforge/common/UsernameCache.java.patch

@@ -0,0 +1,19 @@
+--- ../src-base/minecraft/net/minecraftforge/common/UsernameCache.java
++++ ../src-work/minecraft/net/minecraftforge/common/UsernameCache.java
+@@ -24,6 +24,7 @@
+ import com.google.gson.JsonSyntaxException;
+ 
+ import cpw.mods.fml.relauncher.FMLInjectionData;
++import net.minecraft.server.MinecraftServer;
+ 
+ /**
+  * Caches player's last known usernames
+@@ -39,7 +40,7 @@
+ 
+     private static final Charset charset = Charsets.UTF_8;
+ 
+-    private static final File saveFile = new File( /* The minecraft dir */(File) FMLInjectionData.data()[6], "usernamecache.json");
++    private static final File saveFile = new File( MinecraftServer.serverConfigDir, "usernamecache.json");
+     private static final Gson gson = new GsonBuilder().setPrettyPrinting().create();
+ 
+     private static final Logger log = LogManager.getLogger(UsernameCache.class);