Bug 121498 When datasource/dataset deleted, the datasource/dataset property binding element haven't been deleted
When deleted the datasource/dataset, the datasource/dataset property binding element haven't been deleted. Expected result: This operation must be a transaction.
model/org.eclipse.birt.report.model/src/org/eclipse/birt/report/model/core/Module.java
*/
	public DesignElement getElementByID( long id )
	{
		if ( idMap == null )
			return null;
		return (DesignElement) idMap.get( new Long( id ) );
	}
	/**
	 * Returns the undo/redo stack for this module.
	 * 
	 * @return The "command" stack.
	 */
	public ActivityStack getActivityStack( )
	{
		return activityStack;
	}
	/**
	 * Preprares to save this module. Sets the modification date.
	 */
	public void prepareToSave( )
	{
	}
	/**
	 * Records a successful save.
	 */
	public void onSave( )
	{
		saveState = activityStack.getCurrentTransNo( );
	}
	/**