public class WidgetLoader
This class loads Netbeans Visual Library widgets for a provided named object
and target type. It uses three strategies to load widgets for the target type: custom widget class,
widget consisting of an image of an actor, or widget consisting of a Ptolemy icon.
Load widget of the given PositionableElement and targetType. If there is no widget mapped for the
the target type, it would look for a widget for the target type's parent recursively.
The method would first try finding custom widget class for the targetType. The mappings is
defined in the ObjectWidgets.properties file within widget package. If this fails, it would look for
image of the targetType based on mapping in ImageWidgets.properties file within images package. If this fails too,
it would try loading a Ptolemy icon for the provided NamedObject.
scene - The scene where the widget belongs.
element - The element for which widget is loaded.
targetType - The targetType used to finding appropriate widget mapped to it.
Usually targetType is the same as namedObject's type.