Add HornetQ JMS support

Provide auto-configuration support for HornetQ JMS broker, along with
an additional starter POM.

The connection factory connects to a broker available on the local
machine by default. A configuration switch allows to enable an embedded
mode that starts HornetQ as part of the application.

In such a mode, the spring.hornetq.embedded.* properties provide
additional options to configure the embedded broker. In particular,
message persistence and data directory locations can be specified. It is
also possible to define the queue(s) and topic(s) to create on startup.

Fixes: gh-765

spring-boot-samples/pom.xml

@@ -34,6 +34,7 @@
 		<module>spring-boot-sample-data-rest</module>
 		<module>spring-boot-sample-data-solr</module>
 		<module>spring-boot-sample-flyway</module>
+		<module>spring-boot-sample-hornetq</module>
 		<module>spring-boot-sample-integration</module>
 		<module>spring-boot-sample-jetty</module>
 		<module>spring-boot-sample-liquibase</module>