Refactoring and Adding Tests (#28)

* Introducing repository and refactoring services.
Changing entities to use int keys everywhere.

* Refactoring application services to live in web project and only reference repositories, not EF contexts.

* Cleaning up implementations

* Moving logic out of CatalogController
Moving entity knowledge out of viewmodels.

* Implementing specification includes better for catalogservice

* Cleaning up and adding specification unit tests

src/Web/ViewModels/CatalogItemViewModel.cs

@@ -0,0 +1,14 @@
+using Microsoft.eShopWeb.ApplicationCore.Entities;
+using System.Collections.Generic;
+
+namespace Microsoft.eShopWeb.ViewModels
+{
+
+    public class CatalogItemViewModel
+    {
+        public int Id { get; set; }
+        public string Name { get; set; }
+        public string PictureUri { get; set; }
+        public decimal Price { get; set; }
+    }
+}