Some comment about this pull request.

1. May you refactor the core PageIndexer to write the logs inside the new indexDocuments( StringBuffer ) ? Actually, the logs are written in the IndexationService.write( Document ); but if we want to have a new uniformized system, each indexer should write their own logs inside indexDocuments.

2. Be careful about the code indent: for instance, the bracket have to be on a empty line like this :
   void myMethod( Param param )
   {
   //Content
   }

You can automatize this process by running
mvn formatter:format
on your lutece project; core included.

Alexandre