Introduce a plugin that can copy metadata from another archive in the db.

[soarpasser]

As the title suggests, it would be neat to have a plugin that allows copying the metadata (tags, categories etc.) from an existing archive in the database to another, using the archive ID. This can come in handy when trying to sort archives that have unique tags added by the user themselves, instead of fetched from a website. This can also work as a workaround for when archives lose their tag because of bugs like #942. Example: