NestedProperty support Refactored using NestingItem

Hi Tommi! I've made some changes on the initial pull request, and rebased it on top of your
Expect that it can be useful!

Refactor of initial propoused support of NestedProperties
- Nested properties with null relations implemented over
   NestingItem created by Tommi.
   - Small refactory to not expand properties automatically (addNestedProperty overrided)
 - Removed the Nested Property Depth configuration, as the user
   will configure nested properties directly over EntityContainers
 - Test cases refactored to use this changes.