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
* @param slotID
	 *            the slot from which to remove the content
	 * @param unresolveReference
	 *            status whether to un-resolve the references
	 * @throws SemanticException
	 *             if this content cannot be removed from container.
	 */
	public void remove( DesignElement content, int slotID,
			boolean unresolveReference ) throws SemanticException
	{
		doRemove( content, slotID, unresolveReference, false );
	}
	/**
	 * @see #remove(DesignElement, int, boolean)
	 * @param content
	 *            the element to remove
	 * @param slotID
	 *            the slot from which to remove the content
	 * @param unresolveReference
	 *            status whether to un-resolve the references
	 * @param flag
	 *            Use the flag to indicate whether this method is do with the
	 *            element itself or do with its contents.
	 * @throws SemanticException
	 *             if this content cannot be removed from container.
	 */
	private void doRemove( DesignElement content, int slotID,
			boolean unresolveReference, boolean flag ) throws SemanticException
	{
		assert content != null;