Bug 143430 [CommonNavigator] CommonNavigator requires initialInput to be Adaptable
I have a root nodes that is not Adaptable and that does not fit well with CommonNavigator.getInitialInput which requires (for no real good reason ?) to be Adaptable. Should this not just be an Object ?
bundles/org.eclipse.ui.navigator/src/org/eclipse/ui/navigator/CommonNavigator.java
* <p>
	 * Provides access to the commonViewer used by the current CommonNavigator.
	 * The field will not be valid until after
	 * {@link #init(IViewSite, IMemento)}&nbsp;has been called by the
	 * Workbench.
	 * </p>
	 *  
	 * @return The (already created) instance of Common Viewer.
	 */
	public CommonViewer getCommonViewer() {
		return commonViewer;
	}
	/**
	 * @return The Navigator Content Service which populates this instance of
	 *         Common Navigator
	 */
	public INavigatorContentService getNavigatorContentService() {
		return getCommonViewer().getNavigatorContentService();
	}
	/**
	 * Returns an object which is an instance of the given class
	 * associated with this object. Returns <code>null</code> if
	 * no such object can be found.
	 *
	 * @param adapter the adapter class to look up
	 * @return a object castable to the given class, 
	 *    or <code>null</code> if this object does not
	 *    have an adapter for the given class
	 */
	public Object getAdapter(Class adapter) {