Clearing APC cache is broken

When running ./doctrine orm:clear-cache with the APC cache, it simply won't work because the cache is not shared between the different PHP processes.

So, the php instance run by ./doctrine and the one run by apache are different and won't share their cache. This is an APC feature.

A workaround is needed, other than calling it via apache, or simply remove it. And write it in the documentation.