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/command/ContentCommand.java
/**
	 * Adds a new element into a container. Virtually all elements must reside
	 * in a container. (The term "container" here is generic, it is not the same
	 * as the Container element defined in the XML schema.) Containers are
	 * identified by a container ID. The application creates the element object,
	 * then adds it to the container here. The undo of this operation
	 * effectively deletes the element.
	 * 
	 * @param content
	 *            the element to add
	 * @param slotID
	 *            the slot in which to add the component
	 * @param newPos
	 *            the position index at which the content to be inserted. If
	 *            it's -1, the content will be inserted at the end of the slot.
	 * @throws ContentException
	 *             if the content cannot be added into this container.
	 * @throws NameException
	 *             if the name of the content exists in name space.
	 */
	private void doAdd( DesignElement content, int slotID, int newPos )
			throws ContentException, NameException
	{
		assert content.getContainer( ) == null;
		
		ElementDefn metaData = (ElementDefn) element.getDefn( );
		if ( !metaData.isContainer( ) )
			throw new ContentException( element, slotID,
					ContentException.DESIGN_EXCEPTION_NOT_CONTAINER );
		SlotDefn slotInfo = (SlotDefn) metaData.getSlot( slotID );