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/Commands/Send.cs

@@ -14,7 +14,7 @@ namespace MinecraftClient.Commands
         {
             if (hasArg(command))
             {
-                handler.SendChatMessage(getArg(command));
+                handler.SendText(getArg(command));
                 return "";
             }
             else return CMDDesc;