title: Unrequired property keeps getting data-val-required attribute
body: <p>This is the model with it's validation:</p>
  
  <pre><code>[MetadataType(typeof(TagValidation))]
  public partial class Tag
  {
  }
  
  public class TagValidation
  {
          [Editable(false)]
          [HiddenInput(DisplayValue = false)]
          public int TagId { get; set; }
  
          [Required]
          [StringLength(20)]
          [DataType(DataType.Text)]
          public string Name { get; set; }
      //...
  }
  </code></pre>
  
  <p>Here is the view:</p>
  
  <pre><code>    &lt;h2&gt;Create&lt;/h2&gt;
  
  &lt;script src="@Url.Content("~/Scripts/jquery.validate.min.js")" type="text/javascript"&gt;&lt;/script&gt;
  &lt;script src="@Url.Content("~/Scripts/jquery.validate.unobtrusive.min.js")" type="text/javascript"&gt;&lt;/script&gt;
  
  @using (Html.BeginForm()) {
      @Html.ValidationSummary(true)
      &lt;fieldset&gt;
          &lt;legend&gt;Tag&lt;/legend&gt;
  
          &lt;div&gt;@Html.EditorForModel()&lt;/div&gt;
  
          &lt;p&gt;
              &lt;input type="submit" value="Create" /&gt;
          &lt;/p&gt;
      &lt;/fieldset&gt;
  }
  
  &lt;div&gt;
      @Html.ActionLink("Back to List", "Index")
  &lt;/div&gt;
  </code></pre>
  
  <p>And here is what get's renderd:</p>
  
  <pre><code>&lt;form action="/Tag/Create" method="post"&gt;
      &lt;fieldset&gt;
          &lt;legend&gt;Tag&lt;/legend&gt;
          &lt;div&gt;&lt;input data-val="true" data-val-number="The field TagId must be a number." data-val-required="The TagId field is required." id="TagId" name="TagId" type="hidden" value="" /&gt;
  
          &lt;div class="editor-label"&gt;&lt;label for="Name"&gt;Name&lt;/label&gt;&lt;/div&gt;
          &lt;div class="editor-field"&gt;&lt;input class="text-box single-line" data-val="true" data-val-length="The field Name must be a string with a maximum length of 20." data-val-length-max="20" data-val-required="The Name field is required." id="Name" name="Name" type="text" value="" /&gt; &lt;span class="field-validation-valid" data-valmsg-for="Name" data-valmsg-replace="true"&gt;&lt;/span&gt;&lt;/div&gt;            
      ...
      &lt;/fieldset&gt;
  &lt;/form&gt;
  </code></pre>
  
  <p>The problem is that TagId validation gets generated althoug thare is no Required attribute set on TagId property. Because of that I can't even pass the client-side validation in order to create new Tag in db.
  What am I missing?</p>