Bug 130492 Provide a method to serialize the report with library information.
Currently, when engine generate the report document file, the document does not contain any library information. That will cause many propblem on server side. Model should provide a method to serialize the report with library information to a stream so that the generated report document can contain all information that the report need.
model/org.eclipse.birt.report.model/src/org/eclipse/birt/report/model/core/DesignElement.java
* Returns the container interface for this element if this element is a
	 * container. Derived classes that represent containers must override this.
	 * <p>
	 * Part of: Containment system.
	 * 
	 * @param slot
	 *            the slot ID to get
	 * @return The container interface, or null if this element is not a
	 *         container.
	 */
	public ContainerSlot getSlot( int slot )
	{
		return null;
	}
	/**
	 * Returns a list of user properties defined in this element and somewhere
	 * up the inheritance chain.
	 * 
	 * @return The list of user properties.
	 */
	public List getUserProperties( )
	{
		List props = new ArrayList( );
		DesignElement e = this;
		while ( e != null )
		{
			List prop = e.getLocalUserProperties( );
			if ( prop != null )
			{
				props.addAll( prop );