Assisted rebaseRules generation

Rebase Rules are a *killer* feature in kapp, but the format of them can be fairly verbose, and has a learning curve that makes them a little difficult to approach. It'd be amazing if there was some way to take a current kapp deploy diff and automagically convert that into the necessary kapp-config rebaseRules. This would mean a new user would be modifying things (deleting, and cherry picking accordingly) rather than trying to start from scratch.