Datafeeder: INSPIRE themes are not indexable

[fgravin]

As a user, when I fill one or several INSPIRE themes within the metadata, I expected that those themes are correctly indexed within the catalog.

Description of the issue The theme is filled within the metadata as the translated value, eg in french

<gmd:MD_Keywords>
  <gmd:keyword>
    <gco:CharacterString>Adresses</gco:CharacterString>
  </gmd:keyword> 

Which is not recognized during the indexing.

We should rather use the eng label

<gmd:MD_Keywords>
  <gmd:keyword>
    <gco:CharacterString>Addresses</gco:CharacterString>
  </gmd:keyword> 

or an anchor

<gmd:MD_Keywords>
  <gmd:keyword>
    <gmx:Anchor xlink:href="http://inspire.ec.europa.eu/theme/ad">Adresses</gmx:Anchor>
  </gmd:keyword>