Bug 154828 Item from library contant user properties can't delete
Details: Item from library contant user properties can't delete Step: 1.New a library. 2.Add a label and add a user properites. 3.Public the library. 4.New a report design and use the library 5.Drop the label from library explorer into layout. 6.Try to delete it. Actual result: The label from library contant user properties can't be delete. Exception reuslt: The label can be delete.
model/org.eclipse.birt.report.model/src/org/eclipse/birt/report/model/command/ContentCommand.java
* @throws NameException
	 *             if any element has duplicate name with elements already on
	 *             the design tree.
	 */
	private void addElementNames( DesignElement content ) throws NameException
	{
		
		
		assert content.getContainer( ) != null;
		
		
		NameCommand nameCmd = new NameCommand( module, content );
		nameCmd.addElement( );
		
		for ( int i = 0; i < content.getDefn( ).getSlotCount( ); i++ )
		{
			ContainerSlot slot = content.getSlot( i );
			for ( int j = 0; j < slot.getCount( ); j++ )
			{
				DesignElement tmpElement = slot.getContent( j );
				addElementNames( tmpElement );
			}
		}
	}
	/**
	 * Removes an item from its container. This is equivalent to deleting the
	 * element from the design. Because the element is being deleted, we must
	 * clean up all references to or from the element. References include:
	 * <p>
	 * <ul>