Add simple renderer

Following our discussion, this PR includes:

* It removes the CreateModelResourceListener: now you must explicitly return a ResourceModel from your controller if you want automatic serialization to happen.
* Add a new `ResourceRendererInterface`.
* Add a new `SimpleResourceRenderer` that does a very simple output, which is the default renderer strategy.
* Updated the doc and added a recipe in the cookbook to explain how to add custom data through custom hydrator

The task is to create a HalRenderer. Then, any third party module could create its own renderer (for instance a EmberResourceRenderer) to comply with JavaScript clients.

What do you think?