+ Changed update method to return whether the underlying data structure have indeed been changed.
+ Added PositionChangeListener.
+ Added method for fetching the position of the lowest ID handle from the BaseWidget.
+ Added methods to filter the list of widgets returned by getLeftMostWidget.
+ Added methods to filter the list of widgets returned by getLeftMostWidget
+ Changed the InterfaceManager reference in the TangibleApplication to be static. Changed related getter as well.
+ Abolished precondition from Point on the add method. The parameterized point will see its coordinate system changed to that of the calling point rather then checking a precondition and failing if the coordinate system states are different.