Added support for model autocomplete filter

| Q             | A
| ------------- | ---
| Bug fix?      | no
| New feature?  | yes
| BC breaks?    | yes, but minor (missing and few new methods added to interfaces, changed CSS class in sonata_type_model_autocomplete)
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets | #2360, #2311
| License       | MIT
| SonataDoctrineORMAdmin PR | sonata-project/SonataDoctrineORMAdminBundle#388

Example:
```php
protected function configureDatagridFilters(DatagridMapper $datagridMapper)
{
    $datagridMapper
        ->add('category', 'doctrine_orm_model_autocomplete', array(), null, array(
            'property'=>'title',
        ))
    ;
}
```
it will be better to prefix those variables by ``_`` as some persistents parameters might be named ``context`` (it is the case for the MediaBundle) so this might lead to weird issues