Now it extends GenericTextEditorImpl.
Removed methods already implemented in GenericTextEditorImpl.
Modified constructor for SExpressionEditor.
Removed functionality that GenericTextEditorImpl should not have.
Changed some modifiers to protected so we can use them in extending classes.
Fixed bug when this was using a static variable declared in SImpleTextEditorApp which is no longer used.
Using our SExpressionEditor instead of that custom implementation.