Ban System implemented

The system was based off KMP's ban system.

To ban a player, simply type **/ban [playername] [reason]** and it will automatically ban the user, and kick him from the server.
I added a function in the server, where it checks for different handshake responses, to check if the player is banned. You can check the function below:

```csharp

            if (handshakeReponse == 0)
            {
                    if (bannedNames.Contains(client.playerName) || bannedIPs.Contains(client.ipAddress) || bannedGUIDs.Contains(client.GUID))
                    {
                        client.authenticated = false;
                        handshakeReponse = 5;
                        reason = "You were banned from the server!";
                    }
            }

```
So, whenever a banned player tries to join the server, his handshake will fail, with the reason being 
> You were banned from the server!

PS: GUID is passed via handshake message now.