This class provides interaction with nodes that represent Ptolemy II
objects that are represented on screen as icons, such as attributes
and entities. It provides a double click binding to edit the parameters
of the node, and a context menu containing a command to edit parameters
("Configure"). This adds to the base class the ability to render an
icon for the object being controlled, where the icon is specified
by a contained attribute of class EditorIcon (typically, but not
necessarily named "_icon").