Initial MQTT commit
INTEXT-64 - Polishing

* Update dependency versions
* Add more comments/links
* Remove DocBook usage
INTEXT-89 Fix Inbound Stop When No Server

The reconnection task was not canceled in doStop().
MQTT - Use INT/SPR 4.0.0
MQTT - Update to Spring Integration 4.0.0.M1
Updated MQTTMessageConverter to use new classpath
INT-3239 MQTT Final Polishing For Master Merge

* Final Polishing to move from extensions to master
* Commit history is retained from the extensions
* Docbook Chapter

JIRA: https://jira.springsource.org/browse/INT-3239