Prefer `IHtmlHelper` methods elsewhere in our code

- #847 line 7 sub-bullets
- don't call extension methods from our templates
 - partially addressed in PR #934 (for methods changed there)
- don't reference extension methods from XML comments

src/Microsoft.AspNet.Mvc.Core/Rendering/Html/DefaultEditorTemplates.cs

@@ -227,7 +227,11 @@ namespace Microsoft.AspNet.Mvc.Rendering
 
                 // TODO: add ModelMetadata.HideSurroundingHtml and use here (skip this block)
                 {
-                    var label = html.Label(propertyMetadata.PropertyName).ToString();
+                    var label = html.Label(
+                        propertyMetadata.PropertyName,
+                        labelText: null,
+                        htmlAttributes: null)
+                            .ToString();
                     if (!string.IsNullOrEmpty(label))
                     {
                         divTag.AddCssClass("editor-label");

src/Microsoft.AspNet.Mvc.Core/ViewContext.cs

@@ -65,14 +65,14 @@ namespace Microsoft.AspNet.Mvc
         public bool ClientValidationEnabled { get; set; }
 
         /// <summary>
-        /// Element name used to wrap a top-level message generated by
+        /// Element name used to wrap a top-level message generated by <see cref="IHtmlHelper.ValidationSummary"/> and
-        /// <see cref="HtmlHelperValidationExtensions.ValidationSummary(IHtmlHelper)"/> and other overloads.
+        /// other overloads.
         /// </summary>
         public string ValidationSummaryMessageElement { get; set; }
 
         /// <summary>
-        /// Element name used to wrap a top-level message generated by
+        /// Element name used to wrap a top-level message generated by <see cref="IHtmlHelper.ValidationMessage"/> and
-        /// <see cref="HtmlHelperValidationExtensions.ValidationMessage(IHtmlHelper, string)"/> and other overloads.
+        /// other overloads.
         /// </summary>
         public string ValidationMessageElement { get; set; }