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/ReferencableStructure.java
/**
	 * The list of the cached reference structures. TODO all the issues about
	 * this clients list : add structure, drop structure, replace structure,
	 * broadcase event and so on.
	 */
	protected ArrayList clientStructures = new ArrayList( );
	/*
	 * (non-Javadoc)
	 * 
	 * @see org.eclipse.birt.report.model.api.core.IStructure#isReferencable()
	 */
	public boolean isReferencable( )
	{
		return true;
	}
	/*
	 * (non-Javadoc)
	 * 
	 * @see org.eclipse.birt.report.model.core.IReferencable#addClient(org.eclipse.birt.report.model.core.DesignElement,
	 *      java.lang.String)
	 */
	public void addClient( DesignElement client, String propName )
	{
		clients.add( new BackRef( client, propName ) );
	}
	/*
	 * (non-Javadoc)
	 * 
	 * @see org.eclipse.birt.report.model.core.IReferencable#dropClient(org.eclipse.birt.report.model.core.DesignElement)
	 */