For PlanarFigure subclasses having an arbitrary number of control points (e.g., PlanarPolygon), control points can currently neither be removed nor be added to the object.

The PlanarFigureInteractor should be extended accordingly.

A possible interaction conecpt:

• Point removal: by right-click

• Point adding: when the user hovers over a line segment (of a PlanarFigure which still allows for more control points), a point is temporarily displayed at the mouse position and is added to the polygon if the left mouse button is clicked