Apply HATEOAS module to primary ObjectMapper

Update HypermediaAutoConfiguration to apply the Jackson2HalModule to
the primary ObjectMapper. This restores the behavior of Spring Boot
1.1 where HATEOAS types could be serialized for both `application/json`
and `application/json+hal` content types.

A `spring.hateoas.apply-to-primary-object-mapper` property has also been
provided to opt-out if necessary.

Fixes gh-2147

spring-boot-autoconfigure/src/test/java/org/springframework/boot/autoconfigure/hateoas/HypermediaAutoConfigurationTests.java

@@ -75,19 +75,17 @@ public class HypermediaAutoConfigurationTests {
 
 	@Test
 	public void doesBackOffIfEnableHypermediaSupportIsDeclaredManually() {
-
 		this.context = new AnnotationConfigWebApplicationContext();
 		this.context.register(SampleConfig.class, HypermediaAutoConfiguration.class);
 		this.context.refresh();
-
 		this.context.getBean(LinkDiscoverers.class);
 	}
 
 	@Test
 	public void jacksonConfigurationIsAppliedToTheHalObjectMapper() {
 		this.context = new AnnotationConfigWebApplicationContext();
-		this.context.register(HypermediaAutoConfiguration.class,
-				JacksonAutoConfiguration.class);
+		this.context.register(JacksonAutoConfiguration.class,
+				HypermediaAutoConfiguration.class);
 		EnvironmentTestUtils.addEnvironment(this.context,
 				"spring.jackson.serialization.INDENT_OUTPUT:true");
 		this.context.refresh();