13.2 implentation of game center integration

Implementation includes.

• Authentication fo user in game center.
• Finding a Match
• Sending game state data for starting a game, using game kit real time API. (GKMatchDelegate)

Basic Game State Structure (Draft/Suggestion):

    ┌────────────────────────────────────────────────┐
    │          Example for game life cycle           │
    └────────────────────────────────────────────────┘
    ┌────────────────────────┐
    │ User is authenticated  │
    │   and ready to play    │
    └────────────────────────┘
                 │
                 ├───────────────────────┐
                 │User presses start and │
                 │   sends Game State    │
                 ├───────────────────────┘
                 │
                 ▼
     ┌────────────────────────┐
     │     Waiting screen     │
     └───────────┬────────────┘
                 ├──────────────────────┐
                 │  Received "started"  │
                 │    from all other    │
                 │       players.       │
                 ├──────────────────────┘
                 │
                 ▼
     ┌────────────────────────┐
     │   Game automatically   │
     │         starts         │
     └────────────────────────┘
                 │
                 ├──────────────────────┐
                 │ Received "finished"  │
                 │   from one player.   │
                 ├──────────────────────┘
                 │
                 │
                 ▼
     ┌────────────────────────┐
     │  Show winner or loser  │
     │        screen.         │
     └────────────────────────┘