Middleware for putting large messages to S3

[danfimov]

Since we alreay have some functionality for S3, we can try to implement middleware that will:

• Store large messages (this threshold should be configurable) on S3 before sending them to queue;
• Replace original message with path on S3;
• Before processing it on worker path to S3 should be replaced back to ortiginal message.

I don't think that it should be a part of SQS broker since this functionallity not quite linked to main broker purpose.