Add "copy" default implementation even if the type is not defined

[fernandojsg]

... by doing swallow copy.
The pros is that it's a powerful feature used on UI/Editors a lot, the downside is that it could fail in several cases and if people rely on the default implementation they won't have a clue what is failing there.

[fernandojsg]

I'd close this one, as swallow copy could have many side effects so we won't go into that if not specific use case is defined