Make the MLT disambiguation engine work with the FST linking engine

The Solr MLT disambiguation engine uses the entityhub:site property to check if a suggested Entity originates from the Entityhub Site that is disambiguated.

This entityhub:site is written by the EntityhubLinkingEngine, but not by the FST linking engine as this engine directly uses a SolrCore and does - strictly speaking - not know from (depend on) any Entityhub site.

However STANBOL-1391 added the feature to the FST linking engine to provide origin information for annotations. Those do use the fise:origin property.

This issue is about extending the MLT disambiguation engine to consider fise:origin as a fallback to entityhub:site. This will allow users that want to use MLT disambiguation together with FST linking by configuring the name of the Entityhub site as value of the enhancer.engines.linking.lucenefst.origin property for the FST linking engine.