[WIP] API & ResourceBundle refactoring

Hey folks!

Long story short...

* I've refactored the ResourceController to make it simpler, by extracting some of the stuff to separate helper classes.
* I've moved some of the logic from the SyliusResourceBundle extension to standalone BaseExtension. (extending other bundle DI extension was a bit dirty)
* I've integrated BazingaHateoasBundle and added initial api configurations, the POST & PUT actions are not touched, generally I was mostly playing with the configs, I'll add proper Behat scenarios before continuing.
* I've leveraged the resource services factories (big thank you for @mtotheikle who added them in #749) and thus I removed quite a lot of tedious configuration for the bundles. All is now automatically generated and consistent.

TODO...

* Write Behat scenarios for the API.
* Configure few missing mappings for the models.
* Handle Pagerfanta serialization. (I removed it for a moment, but it is quite easy)
* Handle POST and PUT requests.

Any help appreciated, feel free to send a PR to this branch. Thank you!