Use value with resolved placeholders in all cases
Update Boot plugin to latest snapshot

This enables us to add a classifier to the bootRepackage task and
have spring-xd-dirt spit out its own executable jar. Also validates
that 1.1.2 is going to work in other ways.

Remove spring-xd-exec project (dirt has exec jar now)
XD-1870 Rabbit modules now use addresses

* Remove host and port from RabbitConnectionMixin, RabbitSource & RabbitSink
* Added addresses to RabbitSource & Sink
* Updated Rabbit Acceptance Test.
XD-1788: Validate deployment props
Prevent deletion of content.

Previously, if two opening fences were encountered, no failure was
reported.