Basket persistence (#41)

* Renamed Cart to Basket throughout
* Implemented cookie-based anonymous basket handling and transfer to user upon login. Still need to implement transfer upon registration.

src/Web/Constants.cs

@@ -0,0 +1,7 @@
+namespace Web
+{
+    public static class Constants
+    {
+        public const string BASKET_COOKIENAME = "eShop";
+    }
+}