Make it possible to copy/paste a widget from a layout to another

Importing a complete layout is useful at the begining but once everything is set up, if you add a new widget with a little bit of configuration inside, there is no solution but to repeat three times the operation. It would be great to be able to copy/paste widgets from one layout to another, whether it is on the same document or not, btw.

Also it would be useful to be able to convert a document layout to a generic form layout, for refactoring purpose (when the same layout could be used on distinct document types, for instance)