Sending classes via multiplayer fails without warning

[HomineLudens]

Right now only objects are sent trough the websocket channel using client/server stream. The choice is made for various reasons:

• only a limited amount of data should be sent cyclically
• big structures can be sent from time to time
• nested or self reference object are not allowed

That said, a big warning should be rise on the console when user try to sent classes or self referenced object or list of. Right now it just silently fails, rising a lot of headaches for poor programmers.