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
* <li>The elements that this content contains.
	 * <li>The name space that contains this content.
	 * </ul>
	 * 
	 * @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
	 * @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 );
	}
	/**
	 * 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>
	 * <li>The elements that this content extends.
	 * <li>The elements that extend this content.
	 * <li>The style that this content uses.
	 * <li>The elements that use this style.
	 * <li>The elements that this content contains.
	 * <li>The name space that contains this content.