Default to 'copy' for non-empty fields on merge screen
We've been having a data loss issue on manual merges done by the inbuilt screen (deduper extension is OK) when the person using the form forgets to check all the custom data boxes to carry across
You can see on the screenshot that it defaults to carrying over contributions & activities but not 'middle_name'
I think the default should be to check all boxes where one side has data and the other side does not & propose to change it to make it so - ie (note I haven't touched the addresses - that is a bit more complex & previously thought through I believe)