Use prefix in Logger abstract factory

Force service prefix in LoggerAbstractServiceFactory

- To prevent collisions with other abstract factories, the logger
  abstract factory should require that, when requesting a service, the
  service name be prefixed. I chose "Logger", as that's the service type
  being requested.
- This complements the approach in zendframework/zf2#4253 for cache
  objects.
- Not a BC break, as the LoggerAbstractServiceFactory has not yet been
  released.