[WIP] Extract Doctrine hybrid support

This PR only extracts what's related to hybrid storage into a dedicated bundle. No behavior has been changed, almost nothing has been refactored. Goals:
 * remove what's not related to our PIM catalog business 
 * ease the extraction of this bundle for the community and our future projects

# THIS PR
 - [x] extract base classes
 - [x] activate the bundle
 - [x] rename AkeneoDoctrineHybridSupportBundle to AkeneoDoctrineExtensionBundle
 - [x] rename pim_catalog services to akeneo_doctrine_extensions
 - [x] alias former pim_catalog services to avoid BC breaks
 - [x] make behat pass 
 - [ ] make sure all former pim_catalog services are not used anymore (CE and EE)
 - [ ] make tests pass
 - [ ] add all BC breaks to the changelog
 - [ ] alias pim_catalog.storage_driver and deprecate it
 - [ ] add a note on UPGRADE.md
 - [ ] remove all text occurrences of product or catalog
 
# LATER
## Hybrid storage
 - [ ] add specs to existing classes
 - [ ] move specs into the bundle
 - [ ] documentation !
 - [ ] fix the mapping of the objects so that:
    - [ ] ORM entities should be mapped only for ORM
    - [ ] Mongo documents should be mapped only for Mongo
 - [ ] move what's relevant into a `HybridStorage` directory
 - [ ] a missing orm.yml or mongob.yml file should not make the app crash
 - [ ] extract what can be extracted from AkeneoDoctrineExtensionsExtension et AkeneoDoctrineExtensionsBundle to ease integration (use of simple helper or something like that)
 - [ ] make storage_driver/doctrine/storage.yml file loaded for all bundles ? (not sure, maybe too magic)
 - [ ] clean the constant AkeneoDoctrineExtensionsExtension::DOCTRINE_MONGODB which is useless
 - [ ] define the configuration of the interface with regular Doctrine configuration ?
 - [ ] change the storage `doctrine-mongodb` by `hybrid` 
 
## Repositories
 - [ ] add/make work what @fitn did to ease the definition and override of repositories

## Objects' mapping
 - [ ] add a listener similar to Sylius to switch mapped superclasses to regular objects (ease mapping overriding + get rid of useless empty abstract classes) 

## Extraction
 - [ ] target the extraction of this bundle for 1.4 or 1.5 depending on our needs and the community

Why did you move it?