CHANGE-709 - Refactor logging infrastructure (continuation)

CHANGE-709 - Refactor logging infrastructure (continuation from earlier changes)
- fix chicken/egg problem with log initialization
- add explicit logging messages in more places
- relocate log-delete code to logwriter
<a href='#crh-start'></a><a href='#crh-data-%7B%7D'></a>
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<a href='#crh-end'></a>
The notifier should be injected as it's reused in multiple methods.
```php
public function __construct(notifier $notifier)
{
   $this->notifier = $notifier;
   // ...
}
```