Feature: Copy'n'Paste

[splitbrain]

Currently it seems not to be possible to copy and paste a node with all it's properties. Would be great if either the standard Ctrl-C Ctrl-V key combo would work, or if the context menu would bring up a "duplicate node" item.

When #114 is implemented, whole groups should be copyable, too.

[stan-smith]

👍 recieved.
Pretty busy at the moment, so I'll try get round to this when I can.

[stan-smith]

@splitbrain so the lasso feature is implemented now, should hopefully be much easier to have a copy/paste based off of that.