Get the generated identity value for BulkMerge

[manutiedra]

First I want to thank you for this excellent project. It works great and it is really fast.

The only thing I'd love to have is to be able to get the entities updated with the PK when I call BulkMerge. With BulkInsert I can get the PK using the options.KeepIdentity = false but there is no equivalent property for BulkMerge. It would be awesome if that can be added.