Jobqueue logger

@scottrabin 
Add Wikia\Logger\Loggable trait, and use it in BaseTask
Suggestion: let's consolidate the info calls (because otherwise they spam the log with otherwise-disjoint entries) and instead do

```php
$this->info("Refresh Links", ['cmd' => $cmd, 'exitStatus' => $status, 'output' => $retval]);
```

So: no pre-`wfShellExec` logging, and just dump everything into the context