Plan Migration

⚠️	This feature is not yet implemented.

When a plan is started with changes and has a new version, we need to be able to know what to do with any in-flight documents left over from the previous plan. The default behavior will be to simply ignore them. But at some point we will want to ensure that there is a way of migrating them to the existing plan or alerting the user that there is no applicable migration path. Some cases we need to handle include:

1. The name of the scanner has changed

2. A POTENT step has been re-named

3. A new POTENT step has been added.

4. The source scanner has been removed from the plan.

5. A POTENT step has been removed from the plan