[bs-120] Support for groovy templates

* Added GroovyTemplate.template() utility and static import in webapp CLI, so

        @RequestMapping("/")
        @ResponseBody
        String home(Model model) {
           template "home.html", model
        }

    renders the template in /templates/home.html

[Fixes #49832753]

spring-bootstrap-cli/samples/template.groovy

@@ -0,0 +1,25 @@
+package org.test
+
+import static org.springframework.bootstrap.cli.template.GroovyTemplate.template;
+
+@Component
+class Example implements CommandLineRunner {
+
+	@Autowired
+	private MyService myService
+
+	void run(String... args) {
+		print template("test.txt", ["message":myService.sayWorld()])
+	}
+}
+
+
+@Service
+class MyService {
+
+	String sayWorld() {
+		return "World"
+	}
+}
+
+