Cut/Copy/Paste entity

[0xD21F]

I think it'd be beneficial if you could cut/copy/paste the currently selected entity in the editor using standart shortcuts (and possibly an egui menu item)

[PhaestusFox]

The big issue I see with this is that all components would need to implement clone or copy. We can't just skip any that don't, in case others were dependent on them.

There is also a complicated issue of working out how referenced entities would work/if a resource was referencing them.
The internal referencing could probably be solved with some holistic rules like:

• don't copy ChildOf unless the parent is also copied.
• If the entity was somewhere down the hierarchy (child, grandchild), then point to the corresponding position in the copied tree.
• If the entity is not in the same hierarchy tree, it's probably safe to keep pointing at it. This would probably need to be more restive, like it has no Relationship links, so you don't accedently mess with those when you make the copy