Bug 166015 Refactor designer actions to eclipse command framework
Eclipse command framework provide a more explicit way to manage UI actions contributions, we can take it's advantage to make our actions code more clean and maintainable.
UI/org.eclipse.birt.report.designer.ui/src/org/eclipse/birt/report/designer/internal/ui/editors/schematic/actions/EditBindingAction.java
*/
	protected boolean calculateEnabled( )
	{
		ModuleHandle moduleHandle = SessionHandleAdapter.getInstance( )
				.getReportDesignHandle( );
		return moduleHandle != null
				&& ( !moduleHandle.getVisibleDataSets( ).isEmpty( ) || ( getSelectedElement( ) != null && getSelectedElement( ).getDataSet( ) != null ) );
	}
	private ReportItemHandle getSelectedElement( )
	{
		if ( getTableEditPart( ) != null
				&& getTableEditPart( ).getModel( ) instanceof ReportItemHandle )
		{
			return (ReportItemHandle) getTableEditPart( ).getModel( );
		}
		
		if ( getListEditPart( ) != null
				&& getListEditPart( ).getModel( ) instanceof ReportItemHandle )
		{
			return (ReportItemHandle) getListEditPart( ).getModel( );
		}
		return null;
	}
	/*
	 * (non-Javadoc)
	 * 
	 * @see org.eclipse.jface.action.IAction#run()
	 */
	public void run( )
	{