Backend traits are not applied on an instance when using backend_traits or backendTraits

[ggrossetie]

The following does not work:

class TemplateConverter {
  constructor () {
    this.baseConverter = processor.Html5Converter.create()
    this.templates = templates
    this.backendTraits = {
      basebackend: 'html5',
      outfilesuffix: '.pdf',
      htmlsyntax: 'html',
      supports_templates: true
    }
  }

  convert (node, transform, opts) {
    const template = this.templates[transform || node.node_name]
    if (template) {
      return template(node, this.baseConverter)
    }
    return this.baseConverter.convert(node, transform, opts)
  }
}
processor.ConverterFactory.register(new TemplateConverter(), ['html5'])