Add ability to generate a diff script

[mirhagk]

For situations where you want to analyze what is being run before it's run, you should be able to generate a script that updates and inserts only what is has to. It should also be able to create a rollback script that reverses the changes.

[mirhagk]

From the interactive tool there should also be an additional option which automatically generates a backout script which reverses the changes. Internally this simply swaps the source and target.