[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]

pom.xml

@@ -405,6 +405,11 @@
 				<artifactId>groovy</artifactId>
 				<version>2.1.3</version>
 			</dependency>
+			<dependency>
+				<groupId>org.codehaus.groovy</groupId>
+				<artifactId>groovy-templates</artifactId>
+				<version>2.1.3</version>
+			</dependency>
 			<dependency>
 				<groupId>org.eclipse.jetty</groupId>
 				<artifactId>jetty-webapp</artifactId>