Rename RestTemplates to TestRestTemplate

Rename the RestTemplates to TestRestTemplate to help indicate that it's
primarily intended for testing. Also now extend RestTemplate to allow
direct use, rather than via factory methods.

Fixes gh-599

spring-boot-samples/spring-boot-sample-servlet/src/test/java/sample/servlet/SampleServletApplicationTests.java

@@ -21,7 +21,7 @@ import org.junit.runner.RunWith;
 import org.springframework.beans.factory.annotation.Autowired;
 import org.springframework.boot.autoconfigure.security.SecurityProperties;
 import org.springframework.boot.test.IntegrationTest;
-import org.springframework.boot.test.RestTemplates;
+import org.springframework.boot.test.TestRestTemplate;
 import org.springframework.boot.test.SpringApplicationConfiguration;
 import org.springframework.http.HttpStatus;
 import org.springframework.http.ResponseEntity;
@@ -48,14 +48,14 @@ public class SampleServletApplicationTests {
 
 	@Test
 	public void testHomeIsSecure() throws Exception {
-		ResponseEntity<String> entity = RestTemplates.get().getForEntity(
+		ResponseEntity<String> entity = new TestRestTemplate().getForEntity(
 				"http://localhost:8080", String.class);
 		assertEquals(HttpStatus.UNAUTHORIZED, entity.getStatusCode());
 	}
 
 	@Test
 	public void testHome() throws Exception {
-		ResponseEntity<String> entity = RestTemplates.get("user", getPassword())
+		ResponseEntity<String> entity = new TestRestTemplate("user", getPassword())
 				.getForEntity("http://localhost:8080", String.class);
 		assertEquals(HttpStatus.OK, entity.getStatusCode());
 		assertEquals("Hello World", entity.getBody());