IgniteMessaging in async mode

[Dmitry Karachentsev]

Hi Igniters!

We have in IgniteMessaging interface async support, and it's used only 
for registering/deregistering listeners, not for message sending. But 
user may fall into the case, when connection to destination node was 
lost and user's thread is blocked on 
IgniteMessaging.send()/sendOrdered() methods till 
failureDetectionTimeout is up.

I think, it may be a good idea to support async mode for sending 
messages (and probably without creating separate future for each message).

What do you think?

Thanks!

Dmitry.