support entity manager name auto-completion

[MrMitch]

You can create multiple entity managers in doctrine

doctrine:
    orm:
        auto_generate_proxy_classes: "%kernel.debug%"
        entity_managers:
            foo_mysql:
                naming_strategy: doctrine.orm.naming_strategy.underscore
                connection: mysql
                mappings:
                    FooBarBundle: ~
            foo_sqlserver:
                naming_strategy: doctrine.orm.naming_strategy.underscore
                connection: sqlserver
                mappings:
                    BarFooBundle: ~
        default_entity_manager: foo_mysql

It would be nice if those names (foo_mysql, foo_sqlserver in the example) could be suggested by the auto-complete feature in the getManager($name) method of the ManagerRegistry interface.

[Haehnchen]

related #412

[Haehnchen]

Haehnchen/idea-php-shopware-plugin#30