Bug 167323 [Viewers]Open AbstractTreeViewer for external widget implementors
As reported by Ross Camara AbstractTreeViewer would work for nebula if we would open the API a bit. Boris and I decided that we will do this in 2 steps: 1. open the API 2. moving the Virtual-Support bits from TreeViewer to AbstractTreeViewer when the nebula grid provides virtual support.
bundles/org.eclipse.jface/src/org/eclipse/jface/viewers/ColumnViewer.java
}
	/**
	 * Sets the cell modifier for this column viewer. This method does nothing if editing
	 * is not supported by this viewer.
	 * 
	 * <p>
	 * Since 3.3, an alternative API is available, see
	 * {@link ViewerColumn#setEditingSupport(EditingSupport)} for a more flexible
	 * way of editing values in a column viewer.
	 * </p>
	 * 
	 * @param modifier
	 *            the cell modifier
	 * @since 3.1 (in subclasses, added in 3.3 to abstract class)
	 * @see ViewerColumn#setEditingSupport(EditingSupport)
	 * @see EditingSupport
	 */
	public void setCellModifier(ICellModifier modifier) {
		if (viewerEditor != null) {
			viewerEditor.setCellModifier(modifier);
		}
	}
	/**
	 * Sets the column properties of this column viewer. The properties must
	 * correspond with the columns of the control. They are used to identify the
	 * column in a cell modifier. If editing is not supported by this viewer the
	 * call simply has no effect.
	 * 
	 * <p>
	 * Since 3.3, an alternative API is available, see