Updated clipboard API

[webfiltered]

Just a heads up that there's a PR in to replace the copy & paste methods. I noticed you have some workarounds in place, and I'm hoping this will be good news for you.

Overview of changes

• All items are run through serialize or asSerialisable
• All links to the inputs of copied nodes are included
• Nodes are still cloned as this behaviour is relied on in places, however original IDs are reinserted and copied
• Links use the new Serialisable interface, serialising them as objects like everything else
• Re-linking and ID mutation only occurs when pasting
• Paste returns map of original IDs to pasted items (_paste method only, at present - public API later if no issues)