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
*             if the content cannot be added into this container.
	 * @throws NameException
	 *             if the name of the content exists in name space.
	 */
	public void add( DesignElement content, int slotID, int newPos )
			throws ContentException, NameException
	{
		assert newPos >= 0 || newPos == -1;
		doAdd( content, slotID, newPos );
	}
	/**
	 * Adds a new element into a container. Virtually all elements must reside
	 * in a container. 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
	 * @throws ContentException
	 *             if the content cannot be added into this container.
	 * @throws NameException
	 *             if the name of the content exists in name space.
	 */
	public void add( DesignElement content, int slotID )
			throws ContentException, NameException
	{
		doAdd( content, slotID, -1 );
	}