Added identifier and fetch time product listings; Added persistence to AdafruitShop.

Implemented in AdafruitShop.

AdafruitShop Product listing data now persisted.

AdafruitShop configuration now persisted.

Props/Models/Search/ProductListingInfo.cs

@@ -11,10 +11,8 @@ namespace Props.Models.Search
 
         public uint Hits { get; set; }
 
-        public DateTime LastUpdated { get; set; }
+        public ProductListing ProductListing { get; set; }
 
-        public string ProductUrl { get; set; }
-
-        public string ProductName { get; set; }
+        public string ProductListingIdentifier { get; set; }
     }
 }