Bug 119216 Regression: Group can't be added in layout editor.
Description: Group can't be added in layout editor. Steps to reproduce: 1. Add a table. 2. Right click on the table and find that "insert group" is grayed out.
UI/org.eclipse.birt.report.designer.ui/src/org/eclipse/birt/report/designer/internal/ui/editors/schematic/actions/InsertGroupActionFactory.java
{
	private static final String STACK_MSG_ADD_GROUP = Messages
			.getString( "AddGroupAction.stackMsg.addGroup" ); 
	private Object currentModel;
	private List selection;
	protected static final int POSITION_TOP_LEVEL = 0;
	protected static final int POSITION_INNERMOST = -1;
	protected InsertPositionGroupAction( List selection, String text )