Added model autocomplete filter: doctrine_orm_model_autocomplete

| Q             | A
| ------------- | ---
| Bug fix?      | no
| New feature?  | yes
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets | sonata-project/SonataAdminBundle#2360
| License       | MIT
| SonataAdmin PR        | sonata-project/SonataAdminBundle#2454