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
return null;
	}
	/**
	 * Gets the cached parent element. There will be no parent if either 1) the
	 * element does not extend from another user-defined element, or 2) the
	 * extends element is undefined.
	 * <p>
	 * Part of: Inheritance system.
	 * 
	 * @return parent element
	 */
	public DesignElement getExtendsElement( )
	{
		if ( extendsRef == null )
			return null;
		if ( !extendsRef.isResolved( ) )
			resolveExtends( getRoot( ) );
		return extendsRef.getElement( );
	}
	/**
	 * Resolves the parent element reference.
	 * 
	 * @param module
	 *            the module information needed for the check
	 */
	public void resolveExtends( Module module )
	{
		if ( extendsRef == null || module == null )
			return;
		if ( extendsRef.isResolved( ) )