Keep autofill settings when clear-data-on-exit flag is enabled

[calhix]

Somewhat in line with #1590, I don't think data in the autofill section of settings should be cleared on exit. I admit this could be suggestive but I kind of expect for at least my addresses and payment methods to stay saved since the options to do so are AFAIK not cleared in other browsers normally when you have cookies, browsing history, etc. set to delete on exit.

[Ahrotahn]

There have been requests to have it only delete history or some other subset of the data. When I get some time later I'll see if there's a way to make the flag have a few different options that can be set so people can choose what they want to have removed.