New job log files

Capture output from job submission, poll, kill, event handler commands to new files in the job log directory: 
```
job-submit.(out,err)
job-poll.(out,err)
job-kill.(out,err)
job-event.(out,err)
```

This was discussed by email (at least in part - apparently users expect to see job submission errors in the job log directory).  I noticed while working on the job-kill-at-shutdown problem that we weren't using the command output, which has been captured since the move to multiprocessing.