Ask immediately for port name when exporting graph port

[djdeath]

When working with subgraphs and exporting ports, it's rather tedious to do :

• right click on port
• click export
• select the exported node
• right click
• click rename

in 90% of the cases, you want to rename the exported port name, mostly because you're using generic component which ports' name are often 'in', 'out', etc...

[forresto]

:+1: instead of a modal there, it would be nicer if the input were in-place on top of the export, with the default name selected. Click elsewhere in the graph to accept the default, or type the new name and press enter without needing to select anything.

I'll need to make some way to attach a custom-element to a point in the graph with pan and scale.