Map to bean but tolerate nulls

[ljacqu]

We should have a utility (and realistically, promote it to an alternative BeanProperty) that maps everything it can to a given bean while still accepting nulls. I could imagine Mapper methods alongside the existing ones, something like mapPartial or mapTolerant or something.

Kind of breaks the ConfigMe philosophy of no nulls, but would make debugging easier and also some migrations. Plus I think some people would really want this instead of defensively using Optional and initialized fields everywhere...