Add resubmit method to Job class

[MikeDacre]

Right now the flow of the Job submission process comes to a natural end at job completion. There is no real need for this.

Instead:

• Option to resubmit should be instantly responsive for all failed jobs
• It should ask for confirmation if job succeeded
• It should refuse to continue (without raising an Exception) if the job is currently queued or running, job must be cancelled first.

This should work naturally with the fix to Issue #4 so that the user can update attributes and then resubmit the job.

[MikeDacre]

Done in 0.6.2