Added primitive search mechanism in backend.

Began implementing search mechanism for frontend.

Props/Services/Modules/ISearchManager.cs

@@ -0,0 +1,12 @@
+using System.Collections.Generic;
+using System.Threading.Tasks;
+using Props.Models.Search;
+using Props.Shop.Framework;
+
+namespace Props.Services.Modules
+{
+    public interface ISearchManager
+    {
+        public IEnumerable<ProductListing> Search(string query, SearchOutline searchOutline);
+    }
+}