Theme export: make sure that external styles and that class="..." attributes are exported correctly

  <extension target="org.nuxeo.theme.styling.service" point="pages">
    <themePage name="galaxy/default">
      <defaultFlavour>galaxy</defaultFlavour>
      <flavours append="true">
        <flavour>galaxy</flavour>
        <flavour>galaxy2</flavour>
      </flavours>
      <styles append="true">
        <style>nuxeo_dm_default</style>
        <style>nuxeo_dm_default2</style>
      </styles>
    </themePage>
  </extension>