Provide Tweaks for Defined Jobs

A job definition is a reflection of a policy, hopefully backed up in an SCM or Package Management System. Every ops person knows that there are times when small tweaks need to be made.

I purpose a "tweak" option for all jobs that allow any portion of a job to be changed before running. These changes are a one-off and track like the original in terms of performance metric and in the event log.

This feature can be turned off, but we should leave it on by default. It should be separate from cloning a job or creating a new job.