Add auto configuration for Spring AMQP 1.4 features

This commit adds two additional auto-configuration items that are new
in Spring AMQP 1.4:

* A RabbitMessagingTemplate is automatically created if none is present
* A default RabbitListenerContainerFactory is automatically created if
none is present.

Besides @EnableRabbit is enabled automatically if the necessary classes
are present and a ConnectionFactory is available.

Fixes gh-1495
Improve RabbitMQ support in CLI

This commit deprecates the proprietary EnableRabbitMessaging annotation
in favour of the standard @EnableRabbit introduced as of Spring Rabbit
1.4.

Fixes gh-1494