Added copyPasteProps helper

[gavinmcfarland]

Hi,

I created this function based on the clone function which only copies compatible properties between nodes. It's explicit in properties which are allowed, so it is safer. It also has an option to exclude and include specific properties.

Feel free to make suggestions to modify the actual function, maybe there is a DRYer way to write the function itself.

[gavinmcfarland]

I've been using this helper in my own project. I believe there are still.some edge cases that may need to be covered. For example what happens when properties with mixed values are copied and pasted.

Also we should consider that the default behaviour is. I have thoughts about whether is should (or should not) copy properties like the name by default. Should it match the same as the copy and paste ability in the editor? These are some things for us to consider.