Don't rollback deleted relationships

[DavidPhilip]

During testing I figured out that rollback() also brings back related resources that might've been already deleted and saved (state root.deleted.saved). IMO these have to be excluded from the rollback otherwise you'd end up with a pretty error-prone state.

I can also have a look at how to do this. Anyways I guess it's kind of an edge case. Nevertheless it's something we have to think about. I can provide a user-case if there are more questions.

[danielspaniel]

Boy, that is a great idea @DavidPhilipt . If you can work up a test and even fix it in a PR you will receive a complimentary pet rock with my signature on it.