add log for plugin

ygopro-server.coffee

@@ -3744,3 +3744,4 @@ plugin_list = fs.readdirSync("./plugins")
 for plugin_filename in plugin_list
   plugin_path = process.cwd() + "/plugins/" + plugin_filename
   require(plugin_path)
+  log.info("Plugin loaded:", plugin_filename)

ygopro-server.js

@@ -4831,6 +4831,7 @@
     plugin_filename = plugin_list[m];
     plugin_path = process.cwd() + "/plugins/" + plugin_filename;
     require(plugin_path);
+    log.info("Plugin loaded:", plugin_filename);
   }
 
 }).call(this);