add method to display child progress

[splch]

Summary

creates children_status method for reporting child statuses:

status = job.status(detailed=True)
print(status)

{'total': 2, 'completed': 0, 'failed': 0, 'percentage_complete': 0.0, 'statuses': [<JobStatus.QUEUED: 'job is queued'>, <JobStatus.QUEUED: 'job is queued'>]}
{'total': 2, 'completed': 1, 'failed': 0, 'percentage_complete': 0.5, 'statuses': [<JobStatus.QUEUED: 'job is queued'>, <JobStatus.DONE: 'job has successfully run'>]}
{'total': 2, 'completed': 2, 'failed': 0, 'percentage_complete': 1.0, 'statuses': [<JobStatus.DONE: 'job has successfully run'>, <JobStatus.DONE: 'job has successfully run'>]}

Details and comments