Bug 287139 [CommonNavigator] Add core expression to determine initial activation for NCE
Build ID: 20090619-0625 Steps To Reproduce: Currently, the definition of the Navigator Content Extension via plugin.xml allows to specify the boolean attribute allowByDefault which controls if the contributed content is active by default. It makes sence to change the type of the attribute from boolean to core expression, which will allow to evaluate the default context and show content depending on it. This will ease the control of content and enhance the declarative configuration of CNF and NCEs. More information:
tests/org.eclipse.ui.tests.navigator/src/org/eclipse/ui/tests/navigator/NavigatorTestBase.java
EditorTestHelper.showView(_navigatorInstanceId, false);
	}
	protected void clearAll() throws Exception {
		IProject[] projects = ResourcesPlugin.getWorkspace().getRoot().getProjects();
		for (int i = 0; i < projects.length; i++) {
			projects[i].delete(true, null);
		}
	}
	/**
	 * Use this to not have to wait for the label provider to refresh after changing
	 * the activation.  Otherwise we would have to have a small delay in each test
	 * case which we don't want.
	 */
	protected void refreshViewer() {
		try {
			
			
			
			
			TreeItem[] rootItems = _viewer.getTree().getItems();
			for (int i = 0; i < rootItems.length; i++)
				rootItems[i].setText("");
		} catch (Exception ex) {
			
		}
		_viewer.refresh();
	}
	protected Object verifyMenu(IStructuredSelection sel, String item) {
		MenuManager mm = new MenuManager();