Implements GetByContentType in nucache

src/Umbraco.Tests/LegacyXmlPublishedCache/PublishedContentCache.cs

@@ -548,7 +548,9 @@ namespace Umbraco.Tests.LegacyXmlPublishedCache
 
         public override IEnumerable<IPublishedContent> GetByContentType(PublishedContentType contentType)
         {
-            throw new NotImplementedException();
+            return GetAtRoot()
+                .SelectMany(x => x.DescendantsOrSelf())
+                .Where(x => x.ContentType == contentType);
         }
 
         #endregion

src/Umbraco.Web/PublishedCache/IPublishedCache.cs

@@ -208,8 +208,7 @@ namespace Umbraco.Web.PublishedCache
         /// <returns>The content type, or null.</returns>
         /// <remarks>The alias is case-insensitive.</remarks>
         PublishedContentType GetContentType(string alias);
-
-        // TODO: can we implement this, now? maybe only with NuCache else will throw NotImplemented...
+        
         IEnumerable<IPublishedContent> GetByContentType(PublishedContentType contentType);
     }
 }

src/Umbraco.Web/PublishedCache/NuCache/ContentCache.cs

@@ -388,7 +388,9 @@ namespace Umbraco.Web.PublishedCache.NuCache
 
         public override IEnumerable<IPublishedContent> GetByContentType(PublishedContentType contentType)
         {
-            throw new NotImplementedException();
+            return GetAtRoot()
+                    .SelectMany(x => x.DescendantsOrSelf())
+                    .Where(x => x.ContentType == contentType);
         }
 
         #endregion