Job feature: kill child events jobs if parent job terminates with an error

[athob]

The instance method _ending_todo of a Job object handles the exiting procedure, whether or not the Job completed or exited with an error.

WINGS/src/wpipe/Job.py

Lines 512 to 519 in e3d7519

	def _ending_todo(self):
	if hasattr(sys, "last_value"):
	self.state = repr(sys.last_value)
	else:
	self.state = JOBCOMPSTATE
	self._job.endtime = datetime.datetime.utcnow()
	self._job.timestamp = datetime.datetime.utcnow()
	si.commit()

In the latter case, it only updates the state column in the database to reflect the type of error encountered. Additionally, it should also force-terminates the jobs of any child event it generated and fired.