Add support for groovy utilities in "spring jar"

Also an integration test that uses the (new)
@EnableGroovyTemplates to switch on the template conveniences
in a non-webapp

Fixes gh-990

spring-boot-cli/src/it/java/org/springframework/boot/cli/JarCommandIT.java

@@ -80,5 +80,7 @@ public class JarCommandIT {
 		assertThat(invocation.getStandardOutput(), containsString("/static/static.txt"));
 		assertThat(invocation.getStandardOutput(),
 				containsString("/templates/template.txt"));
+		assertThat(invocation.getStandardOutput(),
+				containsString("Goodbye Mama"));
 	}
 }

spring-boot-cli/src/it/resources/jar-command/jar.groovy

@@ -1,5 +1,6 @@
 package org.test
 
+@EnableGroovyTemplates
 @Component
 class Example implements CommandLineRunner {
 
@@ -12,6 +13,7 @@ class Example implements CommandLineRunner {
 		println getClass().getResource('/resources/resource.txt')
 		println getClass().getResource('/static/static.txt')
 		println getClass().getResource('/templates/template.txt')
+		println template('template.txt', [world:'Mama'])
 	}
 }
 

spring-boot-cli/src/it/resources/jar-command/templates/template.txt

@@ -0,0 +1 @@
+Goodbye ${world}