IVE: Interface move might wrongly grab the connection

I noticed also a small glitch in the interface selection to move it. Depending on where you click inside the triangle itself, it will either move the interface around the box, or select the connection and detach it from the box to move (and re-compute the shape at the end) Actually from usage I prefer the second case : when you select an interface, I think it is better to always detach it and re-compute the points when it is dropped again