    linkView.addLabel(x, y [, opt])

Add a new default label to the link at the coordinates provided. If you need to add a label with custom markup or properties, use the `link.addLabel()` function instead.

This method uses the `linkView.getLabelPosition()` function to determine the new label's `position`. By default, `position.distance` is recorded relative to connection length (as a number in the `[0,1]` range), and `position.offset` is set relative to the connection (as a number). This behavior may be changed by providing an `opt` object with some of the accepted boolean flags:

- `absoluteDistance: true` records `distance` absolutely (as distance from beginning of link)
- `reverseDistance: true` switches `distance` to be calculated from end of link, if `absoluteDistance`
- `absoluteOffset: true` records `offset` absolutely (as `x` and `y` from connection)

The `opt` object passed to the label is recorded as `label.position.args`. The label uses these options during subsequent labelMove interactions.

This function is useful within custom `linkView` event listener definitions:

    var CustomLinkView = joint.dia.LinkView.extend({
        contextmenu: function(evt, x, y) {
            this.addLabel(x, y, {
                absoluteDistance: true,
                reverseDistance: true,
                absoluteOffset: true
            });
        }
    });

    var paper = new joint.dia.Paper({
        // ...
        linkView: CustomLinkView,
        interactive: { vertexAdd: false } // disable default vertexAdd interaction
    });