Add doctrine readmodel support

I'm already using this in my projects. (Although I'm considering using only dbal)
Before I write unit tests I want to make sure you guys want to add this to this library.

Todo
- [x] check if this is something broadway wants to support
- [ ] write tests
- [ ] make it configurable in the bundle
Mhmm, that sounds like a service location. It is not better to inject the actual instance of `ObjectRepository` through constructor? That would allow you to remove the `$class` argument from `__construct()` and make it more testable.