Improved link node management.

Right now, it's very easy to accidentally place excess link nodes on an object while in Link Node Editing mode, and very difficult to remove these excess nodes. Plus, if I want the link node numbers to be in a certain order (for scripting purposes), then it becomes even more difficult. It seems as if when you are in Link Node Editing mode, there should be a new floating dialog window on the screen. This dialog would list all the nodes currently placed, and the order they are placed in. I could select them in this list to re-order their numbering, and also select them on the object to highlight them in this list. In this dialog would also be an 'Add Link Node...' button. Clicking this would add a new link node to the object at its center point. Right-clicking would no longer delete link nodes, but again would instead select them. Click/Drag would move a link node. To delete a link node, you would first have to select it, then press the 'Delete' key, or you could select that node from the list of link nodes and press the 'Delete' key. When you delete a node, you should be asked if you would like the remaining link nodes to re-order themselves to fill in the gap, or if you do not wish them to, incase you have very precise scripting that requires the ordering to stay where they are.