INT-3239 Fix JDK8 Javadoc
INT-3274: build.gradle: BUILD-SNAPSHOT condition

JIRA: https://jira.springsource.org/browse/INT-3274

* Change the `libs-snapshot` repository to `libs-milestone`
* Add condition on `project.version` to check `BUILD-SNAPSHOT` release category
and enable `libs-snapshot` repository
* Remove redundant directories from `mqtt` module
* and one more project property for Spring AMQP version

To test it om master:
1. `gradle.properties -> version=4.0.0.M3`
2. `gradlew clean test --refresh-dependencies -PspringAmqpVersion=1.2.1.RELEASE`
INT-3278 AMQP PubSub Redeclare After Conn. Loss

JIRA: https://jira.springsource.org/browse/INT-3278

A broker-named auto-delete queue is not suitable for use
with a message listener container. If the connection is lost,
the queue is deleted and the container cannot recover its
consumer.

Use an AnonymousQueue, which has the same semantics as the
current queue, but can be redeclared after a connection loss.

Register the channel as a ConnectionListener and redeclare
the queue and binding as necessary.

Note: You cannot currently unregister a listener (AMQP-367)
so if the context is destroyed, the channel will remain a
listener. However, the isRunning() flag can be used to
avoid declaring the channels when in that state.

INT-3278 Polishing

* PR Comments
* Remove the listener when the bean is destroy()ed.