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
{
	/**
	 * Constructs the content command with container element.
	 * 
	 * @param module
	 *            the module
	 * @param container
	 *            the container element
	 */
	public ContentCommand( Module module, DesignElement container )
	{
		super( module, container );
	}
	/**
	 * Adds a new element into a container and specifies the position in the
	 * 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
	 * @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