Failing test for DDC-2306

As of DDC-1734, proxies should have null identifier when the UnitOFWork
refreshes entities and replaces them (marking them as un-managed).
The problem here is that refreshes on entities with same identifier
but different type are still considered same, and the UnitOfWork discards
the proxy instance instead of ignoring it.
Fixing DDC-2306
Adding failing test for DDC-2230

Proxies that implement the Doctrine\Common\PropertyChangedListener are getting eagerly
initialized because the UnitOfWork injects itself into them after they are created.
The test currently fails for what described above, and also verifies if the UoW
is correctly injected in the proxy during lazy loading.
Applying fix for failing test for DDC-2230
Merge pull request #585 from Ocramius/hotfix/DDC-2306

Hotfix/DDC-2306
Merge pull request #589 from Ocramius/hotfix/DDC-2230

Hotfix for DDC-2230