refactor(ShoppingListDetail) : Divide methods to get list detail, and list items

- In order to impreve buying and removing performance, we only get the
list detail, modifying the items list on the client side. Response times
went from ~300ms to 40-50ms.
- Also change REST API, to have /shoplist/{id} to receive a long and be
the default method.
- Added  /shoplist/{id}/items to REST API to retrieve the items in a
shopping list