add whitelisting

[ghost]

I run a bunch of scripts that spawn random vehicles, containers and AI that I don't want grad-persistence to save because they're transient and they'll be randomly created again on a server reboot. Currently I have to hook into all of those scripts and blacklist all these objects on spawn to prevent grad-persistence from including them in saves.

It would be great to be able to reverse this logic and generate a whitelist of objects - via EHs when the players interact with an object, and then have grad-persistence save only whitelisted objects.