Add CuttingLine control to Nodify

[miroiu]

📝 Description of the Change

This PR adds a CuttingLine control to Nodify that removes intersecting connections. The default gesture to start cutting is SHIFT+ALT+LeftClick.

Please note that for the connection style to change when intersecting, it's required to set NodifyEditor.EnableCuttingLinePreview to true. However, this has a great performance impact when many connections are created.

To enable cutting custom connections you must add the connection type to NodifyEditor.CuttingConnectionTypes:

// example adding the Line shape to the connection types that can be cut
NodifyEditor.CuttingConnectionTypes.Add(typeof(System.Windows.Shapes.Line));