Bug 157309 [Viewers] ListViewer should provide insert-method
TableViewer and TreeViewers provide methods to insert a model element and so should ListViewer
bundles/org.eclipse.jface/src/org/eclipse/jface/viewers/AbstractListViewer.java
if (element != null) {
            if (listMapContains(element)) {
				return getControl();
			}
        }
        return null;
    }
	/* (non-Javadoc)
     * Method declared on StructuredViewer.
     */
    protected void doUpdateItem(Widget data, Object element, boolean fullMap) {
        if (element != null) {
            int ix = getElementIndex(element);
            if (ix >= 0) {
                ILabelProvider labelProvider = (ILabelProvider) getLabelProvider();
                listSetItem(ix, getLabelProviderText(labelProvider,element));
            }
        }
    }
    /* (non-Javadoc)
     * Method declared on Viewer.
     */
    public abstract Control getControl();
    /**
     * Returns the element with the given index from this list viewer.
     * Returns <code>null</code> if the index is out of range.
     *
     * @param index the zero-based index
     * @return the element at the given index, or <code>null</code> if the
     *   index is out of range