Bug 267117 [JFace] Provide possibility for subclasses to check if a column is visible in ViewerRow
Currently this is decided by checking with width but this makes Nebula-Grid fail.
bundles/org.eclipse.jface/src/org/eclipse/jface/viewers/ViewerCell.java
*         if the underlying widget implementation doesn't provide this
	 *         information
	 * @since 3.4
	 */
	public Rectangle getImageBounds() {
		return row.getImageBounds(columnIndex);
	}
	/**
	 * Gets the foreground color of the cell.
	 * 
	 * @return the foreground of the cell or <code>null</code> for the default
	 *         foreground
	 * 
	 * @since 3.4
	 */
	public Color getForeground() {
		return row.getForeground(columnIndex);
	}
	/**
	 * Gets the background color of the cell.
	 * 
	 * @return the background of the cell or <code>null</code> for the default
	 *         background
	 * 
	 * @since 3.4
	 */
	public Color getBackground() {
		return row.getBackground(columnIndex);
	}
	/**