create GuiApp.pasteNodes() python function

[bonalex01dev]

This function paste the nodes in the clipboard.
It will be used to reconnect the pasted nodes to the previously selected node as Nuke does. (good time saver)

Known limitation: the nodes are pasted in a very random place probably related to cursor position.

I copy pasted much of the selectAllNodes code and probably left some useless code

Improvements to be done: ability to paste inside a group

Don't hesitate to criticize: these are my very first line of code in C!

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[rodlie]

1. You include several "junk" files from your build
2. I see several references to "selectAllNodes" in your new function, they should probably be fixed/removed

[devernay]

replaced by #674