Fix something in Network module.
* Fix main thread hanging when trying to connect to server.
* Disconnect from server after failed or rejected when trying to connect.
Use C++11 Multithreading library instead of SFML one.
Fix something in Login World and some improvement.
* Fix: "Make New Character Window" show up after selecting a character slot.
* Disconnect from server when clicking cancel button in Character Window.
* Disconnect from server when failed to connect to server.
* Add new packet for communication with Map Server.
* Enable selection using keyboard in Character Window. (Enter to select/make character, Left and Right key for navigation)