Implements World.save and Server.savePlayers()

By: Morgan Humes <mrh9724@lanaddict.com>

paper-server/src/main/java/org/bukkit/craftbukkit/CraftServer.java

@@ -262,7 +262,7 @@ public final class CraftServer implements Server {
                 }
             }
         }
-        
+
         return new CraftWorld(internal);
     }
 
@@ -297,4 +297,8 @@ public final class CraftServer implements Server {
             return null;
         }
     }
+
+    public void savePlayers() {
+        server.d();
+    }
 }