Clone articles inside a collection

Holding Ctrl key when dropping an article above another one will replace the old one with the dropped article.
The new article inherits some custom metadata, including the sublinks.

This is a way to replace the id of an article
The string value `internal-code/content` is used elsewhere, eg https://github.com/guardian/frontend/blob/master/facia-tool/public/js/utils/internal-content-code.js and 
It'd be good to set this value once, in vars.CONST