Ensure DataSource can load database driver

Update DataSource conditional to ensure that the driver class
can actually be loaded by the DataSource. This fixes an issue when
deploying a classic WAR where `org.apache.tomcat.jdbc.pool.DataSource`
is found the parent classloader but the database driver cannot be loaded
because is included as a local `/lib` dependency.
Support single config from ServletInitializer

Update SpringBootServletInitializer with separate getConfigClass() and
getAdditionalConfigClasses() methods. This change makes it easier to
use the SpringBootServletInitializer with the common use case of a
single config class.
Add JMS autoconfig support

* application.properties support for spring.jms and spring.activemq

* more tests to verify ActiveMQConnectionFactory pooling

* Groovy support and simple sample with activemq

* Groovy detection mechanism is @EnableJmsMessaging annotation
Add support for Spring Rabbit (via Spring AMQP) to Boot

- If RabbitTemplate is on the classpath, turn on autodetection.
- Create a RabbitTemplate, a Rabbit ConnectionFactory, and a RabbitAdmin is spring.rabbitmq.dynamic:true
- Enable some **spring.rabbitmq** properties like host, port, username, password, and dynamic
- Add tests to verify functionality
- Add Groovy CLI functionality. Base it on @EnableRabbitMessaging. Add spring-amqp to the path.
- Create rabbit.groovy test to prove it all works.
- Make Queue and TopicExchange top-level Spring beans in rabbit.groovy test script
Fix test