Account list file support

Accounts can be stored in a file and used while (re)connecting
+ Check that the server IP is valid (avoid /connect <player>)
+ Fix command prompt not exiting while exiting the server
+ SendChatMessage() -> SendText() method name change

MinecraftClient/ChatBot.cs

@@ -81,7 +81,7 @@ namespace MinecraftClient
         protected bool SendText(string text)
         {
             ConsoleIO.WriteLineFormatted("§8BOT:" + text, false);
-            return handler.SendChatMessage(text);
+            return handler.SendText(text);
         }
 
         /// <summary>