AMQP-429: Change `@SendTo` logic to `Address`

JIRA: https://jira.spring.io/browse/AMQP-429

Since `@SendTo` can apply only `String` values, but from other side `Address` can parse that `String`,
there is no stops to use `Address` object as a `replyToAddress`.
Now to send a result of `@RabbitListener` method to some specific `replyTo` you can specify it like this:
```
@RabbitListener(queues = "test.sendTo")
@SendTo("direct:///test.sendTo.reply")
public String capitalizeAndSendTo(String foo) {
	return foo.toUpperCase();
}
```

* Add integration test
* In addition remove redundant `@RabbitListener.responseRoutingKey()`
This `Address` abstraction looks pretty bogus to me. The type is never used. With this commit, the type will be coerced to "direct", but it won't matter because it wont' be used.

This address format has not previously been exposed to users and I don't think we should do so now.

I think we need to come up with another abstraction to define the exchange/routingKey for the default replyTo.