Bug 126839 [DataBinding] IObservable refactoring
bundles/org.eclipse.jface.databinding/src/org/eclipse/jface/internal/databinding/viewers/TreeViewerUpdatableTreeExtended.java
public Image getColumnImage(Object element, int columnIndex) {
			if (columnIndex<treeViewerDescription.getColumnCount(element.getClass()) && columnIndex>=0) {
				Column column = getColumn(element.getClass(), columnIndex);
				IConverter converter = column.getConverter();
				if (converter.getTargetType().equals(ViewerLabel.class)) {
					ViewerLabel viewerLabel = (ViewerLabel) getConvertedValue(
							element, column);
					return viewerLabel.getImage();
				}
			}
			return null;
		}
		public String getColumnText(Object element, int columnIndex) {
			Object convertedValue=null;
			if (columnIndex<treeViewerDescription.getColumnCount(element.getClass()) && columnIndex>=0) {
			  Column column = getColumn(element.getClass(), columnIndex);
			  convertedValue = getConvertedValue(element, column);
			  IConverter converter = column.getConverter();
			  if (converter.getTargetType().equals(ViewerLabel.class)) {
					ViewerLabel viewerLabel = (ViewerLabel) convertedValue;
					return viewerLabel.getText();
			  }				
			}
			return convertedValue==null? "": (String) convertedValue; 
		}
		
		public Image getImage(Object element) {			
			return getColumnImage(element,0);
		}
		public String getText(Object element) {