Gearman service returns GearmanJobStatus from addJob

Gearman::addJob now returns a GearmanJobStatus object which contains the job handle and Gearman client return code associated with the task.

Example:
```php
$jobStatus = $this->gearman->addJob($job, true, GearmanJobInterface::PRIORITY_LOW);
// Access the job handle string
$jobStatus->getJobHandle();
// Access the Gearman client returnCode() value
$jobStatus->getReturnCode();
if (!$jobStatus->isSuccessful()) {
    // Log the error.  Additional details in $jobStatus->getFunctionName() and $jobStatus->getWorkload()
}
```