Add support for beans{} in CLI scripts

User can add (a single) beans{} DSL declaration (see GroovyBeanDefinitionReader
in Spring 4 for more detail) anywhere at the top level of an application source
file. It will be compiled to a closure and fed in to the application context
through a GroovyBeanDefinitionReader. Cool!

The example spring-boot-cli/samples/beans.groovy runs in an integration test
and passes (see SampleIntegrationTests).

spring-boot-cli/src/test/java/org/springframework/boot/cli/SampleIntegrationTests.java

@@ -54,6 +54,13 @@ public class SampleIntegrationTests {
 				output.contains("Hello World! From " + scriptUri));
 	}
 
+	@Test
+	public void beansSample() throws Exception {
+		this.cli.run("beans.groovy");
+		String output = this.cli.getHttpOutput();
+		assertTrue("Wrong output: " + output, output.contains("Hello World!"));
+	}
+
 	@Test
 	public void templateSample() throws Exception {
 		String output = this.cli.run("template.groovy");