Allow to define indexing configuration

We must be able to define :

• what Document types can be indexed (use a facet?)
  -> all document types (non system) are indexed

• what fields should be indexed (or at least what schemas)
  -> all fields are indexed

• field configuration
  -> there is a default mapping where we mark some field as being fulltext, we also setup a proper index to search on path
  this can be overridden by the elasticSearchIndex EP