Refactoring and Adding Tests (#58)

* Moving Identity seeding to its own class and method.

* Adding tests for AddItem

* Added catalog api controller and functional tests
Added and cleaned up some comments

* Adding integration tests for OrderRepository

* Getting integration test for order working with inmemory db

src/ApplicationCore/Entities/BaseEntity.cs

@@ -1,5 +1,7 @@
 namespace Microsoft.eShopWeb.ApplicationCore.Entities
 {
+    // This can easily be modified to be BaseEntity<T> and public T Id to support different key types.
+    // Using non-generic integer types for simplicity and to ease caching logic
     public class BaseEntity
     {
         public int Id { get; set; }

src/ApplicationCore/Entities/BasketItem.cs

@@ -5,6 +5,5 @@
         public decimal UnitPrice { get; set; }
         public int Quantity { get; set; }
         public int CatalogItemId { get; set; }
-//        public CatalogItem Item { get; set; }
     }
 }