Feature: Copy job with new workflow version

A use case that came up in yesterday's meeting was to re-run previous jobs with a new version of the workflow. Rather than expecting users to repeat their input data object, we should add a method to copy an existing job to a new job, specifying an alternate workflow version.

Assuming the job order is compatible with the new version, there will be minimal changes to the data model to accommodate this. The `Job` -> `JobFileStageGroup` relationship is 1:1, so we'd need to make that 1:many or copy the stage group as well.