addActionTarget = "[String] widget name, [Constant] event,[Method] execute method" [String] is the name of the widget [Constant] the event to listen on [Method] the method signature
A backspace event only occurs in Edit controls.
If the caret is at the start of the label and the backpace key is pressed, then the backspace event is generated.
If the caret is at the start of the label and the left arrow key is pressed, then the backspace event is generated.
To demostrate the backspace event, on the forwardspace event we will request focus to the next widget,
and on the backspace event we will request focus to the previous widget
The Widget, 'edit2', will execute the method 'requestFocus'
On the forwardspace event we execute edit2.requestFocus="edit3", the Widget 'edit3' gains focus
On the backspace event we execute edit2.requestFocus="edit1", the Widget 'edit1' gains focus
To handle more than one event, we append them to the addActionTarget, the addActionTarget accepts parameters in tuples (3,6,9,etc...)