title: Returned json unexpected, has "links" spelled as "_links" and structure different, in Spring hateoas
body: <p>As the title says, I have a resource object <code>Product</code> extending <code>ResourceSupport</code>. However, the responses I receive have the property "_links" instead of "links" and have a different structure.</p>
  
  <pre><code>{
    "productId" : 1,
    "name" : "2",
    "_links" : {
      "self" : {
        "href" : "http://localhost:8080/products/1"
      }
    }
  }
  </code></pre>
  
  <p>Based on the <a href="https://github.com/spring-projects/spring-hateoas/blob/master/readme.md" rel="noreferrer">HATEOAS Reference</a>, the expected is:</p>
  
  <pre><code>{
    "productId" : 1,
    "name" : "2",
    "links" : [
      {
        "rel" : "self"
        "href" : "http://localhost:8080/products/1"
      }
    ]
  }
  </code></pre>
  
  <p><strong>Was this intended? Is there a way to change it, or at leas the "link" if not the structure?</strong></p>
  
  <p>I added the selfLink through the following snippet:</p>
  
  <pre><code>product.add(linkTo(ProductController.class).slash(product.getProductId()).withSelfRel());
  </code></pre>
  
  <p>I am using spring boot with the following build file:</p>
  
  <pre><code>dependencies {
      compile ("org.springframework.boot:spring-boot-starter-data-rest") {
          exclude module: "spring-boot-starter-tomcat"
      }
  
      compile "org.springframework.boot:spring-boot-starter-data-jpa"
      compile "org.springframework.boot:spring-boot-starter-jetty"
      compile "org.springframework.boot:spring-boot-starter-actuator"
  
      runtime "org.hsqldb:hsqldb:2.3.2"
  
      testCompile "junit:junit"
  }
  </code></pre>