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
{
		if ( derived == null )
			return;
		for ( int i = 0; i < derived.size( ); i++ )
		{
			DesignElement child = (DesignElement) derived.get( i );
			list.add( child );
			child.gatherDescendents( list );
		}
	}
	/**
	 * Checks if the element has defined any user properties. Checks only this
	 * element, not its parents.
	 * 
	 * @return True if the element has user properties, false if not.
	 */
	public boolean hasUserProperties( )
	{
		return userProperties != null && !userProperties.isEmpty( );
	}
	/**
	 * Checks if this element has any locally-defined property values.
	 * 
	 * @return True if the element has property values, false if not.
	 */
	public boolean hasLocalPropertyValues( )
	{
		return !propValues.isEmpty( );
	}
	/**