Introducing super basic health check for cart service (#44)

* Introducing super basic health check for cart service
  - Generated C# proto implementation for grpc health check
  - Moved all C# protos to a dedicated folder
  - Implemented basic health checking to ping CartStore (which is Redis in default implementation)
  - Base plumbing for health checks

* Introducing super basic health check for cart service

- Generated C# proto implementation for grpc health check
- Moved all C# protos to a dedicated folder
- Implemented basic health checking to ping CartStore (which is Redis in default implementation)
- Base plumbing for health checks

* Changing Ping health probe to call Redis Cache Ping method

src/cartservice/interfaces/ICartStore.cs

@@ -24,5 +24,7 @@ namespace cartservice.interfaces
         Task EmptyCartAsync(string userId);
 
         Task<Hipstershop.Cart> GetCartAsync(string userId);
+
+        bool Ping();
     }
 }