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/Exceptions/CatalogImageMissingException.cs

@@ -1,29 +0,0 @@
-using System;
-
-namespace ApplicationCore.Exceptions
-{
-    /// <summary>
-    /// Note: No longer required.
-    /// </summary>
-    public class CatalogImageMissingException : Exception
-    {
-        public CatalogImageMissingException(string message,
-            Exception innerException = null)
-            : base(message, innerException: innerException)
-        {
-        }
-        public CatalogImageMissingException(Exception innerException)
-            : base("No catalog image found for the provided id.", 
-                  innerException: innerException)
-        {
-        }
-
-        public CatalogImageMissingException() : base()
-        {
-        }
-
-        public CatalogImageMissingException(string message) : base(message)
-        {
-        }
-    }
-}