public static PageTemplateRegistry toRegistry(PageTemplatesConfig config) {
        List<NamedReader> pageReaders=new ArrayList<>();
        int pageNumber=0;
        for (String pageString : config.page())
            pageReaders.add(new NamedReader("page[" + pageNumber++ + "]",new StringReader(pageString)));
        return new PageTemplateXMLReader().read(pageReaders,false);
    }
Creates a new page template registry from the content of a config and returns it.
The returned registry will <b>not</b> be frozen. This should be done, by calling freeze(), before it is used.
container-search/src/main/java/com/yahoo/search/pagetemplates/config/PageTemplateConfigurer.java