Correct 'Configuration Priority' topic.

Right now the configuration is applied not applied in the way is described in the doc. Key lines are:

- `$this->serviceManagers[$key]['configuration']['merged_config'] = $config[$sm['config_key']];` where the merged config is added to the  config array
- `foreach ($this->serviceManagers[$key]['configuration'] as $configs) {` where the config is actually merged.