[*] Smart Views - Smart views can access nested relationship

[VincentMolinie]

Pull Request checklist:

• [X] Write an explicit title for the Pull Request
• [X] Write changes made in the CHANGELOG.md
• [ ] Create automatic tests
• [ ] No automatic tests failures
• [X] Test manually the implemented changes
• [X] Review my own code (indentation, syntax, style, simplicity, readability)
• [ ] Wonder if you can improve the existing code

[VincentMolinie]

P2 - Plugify can't get his smart view to work properly

[VincentMolinie]

To add more context about how JSON API works: First thing we need to know is that if in a relationships, there is a link specified even if the data are retrieved in the included, Ember Data will do a GET request on the url. So link must be here ONLY if the data is not included. Then where there is data in relationships { data: { id: '1', type: 'student'}} and a link the data will always be the first one to be called. If none of them is specified, the relation is considered as null.

[arnaudbesnier]

Let's keep this for later. We need stability now and I don't want to introduce unecessary feature. Especially on the liana side.